Use zlib information to verify compressed content before using it

- Detect and prevent an xref table/stream at a certain offset from being read twice; malformed xref tables with circular references could otherwise cause the table-reading to loop forever.
- Another approach could be to prevent TryReadTableAtOffset from changing the bytes' CurrentOffset to the lastObjPosition in its attempt to read a table (eg restore CurrentOffset after the attempt to read a Table) so the outer bytes-loop could continue its search through the entire bytes unaffected.

.gitignore

@@ -249,3 +249,4 @@ _Pvt_Extensions
 
 /docs/doxygen
 /tools/UglyToad.PdfPig.ConsoleRunner/Properties/launchSettings.json
+/src/UglyToad.PdfPig.Tests/Images/Files/Pdf/indexed-png-with-mask.png

src/UglyToad.PdfPig.Core/TransformationMatrix.cs

@@ -224,9 +224,18 @@
         [Pure]
         public double TransformX(double x)
         {
-            var xt = A * x + C * 0 + E;
+            return A * x + E; // + C * 0 
+        }
 
-            return xt;
+
+        /// <summary>
+        /// Transform an Y coordinate using this transformation matrix.
+        /// </summary>
+        /// <param name="y">The Y coordinate.</param>
+        /// <returns>The transformed Y coordinate.</returns>
+        public double TransformY(double y)
+        {
+            return D * y + F;
         }
 
         /// <summary>

src/UglyToad.PdfPig.DocumentLayoutAnalysis/Clustering.cs

@@ -216,71 +216,37 @@
                 yield return group.Select(i => elements[i]).ToList();
             }
         }
-
-        /// <summary>
-        /// Group elements using Depth-first search.
-        /// <para>https://en.wikipedia.org/wiki/Depth-first_search</para>
-        /// </summary>
-        /// <param name="edges">The graph. edges[i] = j indicates that there is an edge between i and j.</param>
-        /// <returns>A List of HashSets containing the grouped indexes.</returns>
-        internal static List<HashSet<int>> GroupIndexes(int[] edges)
+        
+        internal static List<List<int>> GroupIndexes(int[] edges)
         {
-            int[][] adjacency = new int[edges.Length][];
+            // Improved thanks to https://github.com/UglyToad/PdfPig/issues/1178
+            var adjacency = new List<int>[edges.Length];
             for (int i = 0; i < edges.Length; i++)
             {
-                HashSet<int> matches = new HashSet<int>();
-                if (edges[i] != -1) matches.Add(edges[i]);
-                for (int j = 0; j < edges.Length; j++)
-                {
-                    if (edges[j] == i) matches.Add(j);
-                }
-                adjacency[i] = matches.ToArray();
+                adjacency[i] = new List<int>();
             }
 
-            List<HashSet<int>> groupedIndexes = new List<HashSet<int>>();
+            // one pass O(n) 
+            for (int i = 0; i < edges.Length; i++)
+            {
+                int j = edges[i];
+                if (j != -1)
+                {
+                    // i <-> j
+                    adjacency[i].Add(j);
+                    adjacency[j].Add(i);
+                }
+            }
+
+            List<List<int>> groupedIndexes = new List<List<int>>();
             bool[] isDone = new bool[edges.Length];
 
             for (int p = 0; p < edges.Length; p++)
             {
-                if (isDone[p]) continue;
-                groupedIndexes.Add(DfsIterative(p, adjacency, ref isDone));
-            }
-            return groupedIndexes;
-        }
-
-        /// <summary>
-        /// Group elements using Depth-first search.
-        /// <para>https://en.wikipedia.org/wiki/Depth-first_search</para>
-        /// </summary>
-        /// <param name="edges">The graph. edges[i] = [j, k, l, ...] indicates that there is an edge between i and each element j, k, l, ...</param>
-        /// <returns>A List of HashSets containing the grouped indexes.</returns>
-        internal static List<HashSet<int>> GroupIndexes(int[][] edges)
-        {
-            int[][] adjacency = new int[edges.Length][];
-            for (int i = 0; i < edges.Length; i++)
-            {
-                HashSet<int> matches = new HashSet<int>();
-                for (int j = 0; j < edges[i].Length; j++)
+                if (isDone[p])
                 {
-                    if (edges[i][j] != -1) matches.Add(edges[i][j]);
+                    continue;
                 }
-
-                for (int j = 0; j < edges.Length; j++)
-                {
-                    for (int k = 0; k < edges[j].Length; k++)
-                    {
-                        if (edges[j][k] == i) matches.Add(j);
-                    }
-                }
-                adjacency[i] = matches.ToArray();
-            }
-
-            List<HashSet<int>> groupedIndexes = new List<HashSet<int>>();
-            bool[] isDone = new bool[edges.Length];
-
-            for (int p = 0; p < edges.Length; p++)
-            {
-                if (isDone[p]) continue;
                 groupedIndexes.Add(DfsIterative(p, adjacency, ref isDone));
             }
             return groupedIndexes;
@@ -290,22 +256,33 @@
         /// Depth-first search
         /// <para>https://en.wikipedia.org/wiki/Depth-first_search</para>
         /// </summary>
-        private static HashSet<int> DfsIterative(int s, int[][] adj, ref bool[] isDone)
+        private static List<int> DfsIterative(int s, List<int>[] adj, ref bool[] isDone)
         {
-            HashSet<int> group = new HashSet<int>();
-            Stack<int> S = new Stack<int>();
+            List<int> group = new List<int>();
+            Stack<int> S = new Stack<int>(4);
             S.Push(s);
 
+            isDone[s] = true;
             while (S.Count > 0)
             {
                 var u = S.Pop();
-                if (!isDone[u])
+                group.Add(u);
+
+#if NET
+                var currentAdj = System.Runtime.InteropServices.CollectionsMarshal.AsSpan(adj[u]);
+                int count = currentAdj.Length;
+#else
+                var currentAdj = adj[u];
+                int count = currentAdj.Count;
+#endif
+                for (int i = 0; i < count; ++i)
                 {
-                    group.Add(u);
-                    isDone[u] = true;
-                    foreach (var v in adj[u])
+                    var v = currentAdj[i];
+                    ref bool done = ref isDone[v];
+                    if (!done)
                     {
                         S.Push(v);
+                        done = true;
                     }
                 }
             }

src/UglyToad.PdfPig.DocumentLayoutAnalysis/DuplicateOverlappingTextProcessor.cs

@@ -68,25 +68,11 @@
                     // update textSequence?
 
                     // update font details to bold
-                    var fontDetails = new FontDetails(letter.Font.Name, true, letter.Font.Weight, letter.Font.IsItalic);
-
-                    var newLetter = new Letter(letter.Value,
-                        letter.GlyphRectangle,
-                        letter.StartBaseLine,
-                        letter.EndBaseLine,
-                        letter.Width,
-                        letter.FontSize,
-                        fontDetails,
-                        letter.RenderingMode,
-                        letter.StrokeColor,
-                        letter.FillColor,
-                        letter.PointSize,
-                        letter.TextSequence);
 
                     // update markedContentStack?
 
                     // update letters
-                    cleanLetters[duplicatesOverlappingIndex] = newLetter;
+                    cleanLetters[duplicatesOverlappingIndex] = letter.AsBold();
                 }
             }
 

src/UglyToad.PdfPig.DocumentLayoutAnalysis/TextExtractor/ContentOrderTextExtractor.cs

@@ -60,11 +60,12 @@
                     letter = new Letter(
                         " ",
                         letter.GlyphRectangle,
+                        letter.GlyphRectangleLoose,
                         letter.StartBaseLine,
                         letter.EndBaseLine,
                         letter.Width,
                         letter.FontSize,
-                        letter.Font,
+                        letter.GetFont()!,
                         letter.RenderingMode,
                         letter.StrokeColor,
                         letter.FillColor,

src/UglyToad.PdfPig.Fonts/CompactFontFormat/CharStrings/Type2CharStringParser.cs

@@ -770,6 +770,8 @@ namespace UglyToad.PdfPig.Fonts.CompactFontFormat.CharStrings
                 }
             }
 
+            values.TrimExcess();
+
             return new Type2CharStrings.CommandSequence(values, commandIdentifiers);
         }
 

src/UglyToad.PdfPig.Fonts/CompactFontFormat/Charsets/CompactFontFormatIsoAdobeCharset.cs

@@ -257,6 +257,10 @@
                 gidToStringIdAndNameMap[gid++] = pair;
             }
 
+#if NET
+            gidToStringIdAndNameMap.TrimExcess();
+#endif
+
             glyphIdToStringIdAndName = gidToStringIdAndNameMap;
         }
 

src/UglyToad.PdfPig.Fonts/TrueType/Tables/GlyphDataTable.cs

@@ -121,14 +121,23 @@
 
             for (var i = 0; i < glyphCount; i++)
             {
-                if (offsets[i + 1] <= offsets[i])
+                var offset = offsets[i];
+
+                if (offsets[i + 1] <= offset)
                 {
                     // empty glyph
                     result[i] = emptyGlyph;
                     continue;
                 }
 
-                data.Seek(offsets[i]);
+                // Invalid table, just sub in the empty glyph
+                if (offset >= data.Length)
+                {
+                    result[i] = emptyGlyph;
+                    continue;
+                }
+
+                data.Seek(offset);
 
                 var contourCount = data.ReadSignedShort();
 

src/UglyToad.PdfPig.Fonts/UglyToad.PdfPig.Fonts.csproj

@@ -7,6 +7,7 @@
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <SignAssembly>true</SignAssembly>
     <AssemblyOriginatorKeyFile>..\pdfpig.snk</AssemblyOriginatorKeyFile>
+    <Nullable>annotations</Nullable>
   </PropertyGroup>
   <ItemGroup>
     <None Remove="Resources\AdobeFontMetrics\*" />

src/UglyToad.PdfPig.Tests/ContentStream/IndirectReferenceTests.cs

@@ -1,6 +1,7 @@
 namespace UglyToad.PdfPig.Tests.ContentStream
 {
     using PdfPig.Core;
+    using System.Globalization;
 
     public class IndirectReferenceTests
     {
@@ -33,50 +34,59 @@
         [Fact]
         public void IndirectReferenceHashTest()
         {
-            var reference0 = new IndirectReference(1574, 690);
-            Assert.Equal(1574, reference0.ObjectNumber);
-            Assert.Equal(690, reference0.Generation);
+            CultureInfo lastCulture = CultureInfo.CurrentCulture;
+            CultureInfo.CurrentCulture = new CultureInfo("en-US");
+            try
+            {
+                var reference0 = new IndirectReference(1574, 690);
+                Assert.Equal(1574, reference0.ObjectNumber);
+                Assert.Equal(690, reference0.Generation);
 
-            var reference1 = new IndirectReference(-1574, 690);
-            Assert.Equal(-1574, reference1.ObjectNumber);
-            Assert.Equal(690, reference1.Generation);
+                var reference1 = new IndirectReference(-1574, 690);
+                Assert.Equal(-1574, reference1.ObjectNumber);
+                Assert.Equal(690, reference1.Generation);
 
-            var reference2 = new IndirectReference(58949797283757, 16);
-            Assert.Equal(58949797283757, reference2.ObjectNumber);
-            Assert.Equal(16, reference2.Generation);
+                var reference2 = new IndirectReference(58949797283757, 16);
+                Assert.Equal(58949797283757, reference2.ObjectNumber);
+                Assert.Equal(16, reference2.Generation);
 
-            var reference3 = new IndirectReference(-58949797283757, ushort.MaxValue);
-            Assert.Equal(-58949797283757, reference3.ObjectNumber);
-            Assert.Equal(ushort.MaxValue, reference3.Generation);
+                var reference3 = new IndirectReference(-58949797283757, ushort.MaxValue);
+                Assert.Equal(-58949797283757, reference3.ObjectNumber);
+                Assert.Equal(ushort.MaxValue, reference3.Generation);
 
-            var reference4 = new IndirectReference(140737488355327, ushort.MaxValue);
-            Assert.Equal(140737488355327, reference4.ObjectNumber);
-            Assert.Equal(ushort.MaxValue, reference4.Generation);
+                var reference4 = new IndirectReference(140737488355327, ushort.MaxValue);
+                Assert.Equal(140737488355327, reference4.ObjectNumber);
+                Assert.Equal(ushort.MaxValue, reference4.Generation);
 
-            var reference5 = new IndirectReference(-140737488355327, ushort.MaxValue);
-            Assert.Equal(-140737488355327, reference5.ObjectNumber);
-            Assert.Equal(ushort.MaxValue, reference5.Generation);
+                var reference5 = new IndirectReference(-140737488355327, ushort.MaxValue);
+                Assert.Equal(-140737488355327, reference5.ObjectNumber);
+                Assert.Equal(ushort.MaxValue, reference5.Generation);
 
-            var ex0 = Assert.Throws<ArgumentOutOfRangeException>(() => new IndirectReference(140737488355328, 0));
-            Assert.StartsWith("Object number must be between -140,737,488,355,327 and 140,737,488,355,327.", ex0.Message);
-            var ex1 = Assert.Throws<ArgumentOutOfRangeException>(() => new IndirectReference(-140737488355328, 0));
-            Assert.StartsWith("Object number must be between -140,737,488,355,327 and 140,737,488,355,327.", ex1.Message);
-            
-            var ex2 = Assert.Throws<ArgumentOutOfRangeException>(() => new IndirectReference(1574, -1));
-            Assert.StartsWith("Generation number must not be a negative value.", ex2.Message);
-            
-            // We make sure object number is still correct even if generation is not
-            var reference6 = new IndirectReference(1574, int.MaxValue);
-            Assert.Equal(1574, reference6.ObjectNumber);
-            
-            var reference7 = new IndirectReference(-1574, ushort.MaxValue + 10);
-            Assert.Equal(-1574, reference7.ObjectNumber);
+                var ex0 = Assert.Throws<ArgumentOutOfRangeException>(() => new IndirectReference(140737488355328, 0));
+                Assert.StartsWith("Object number must be between -140,737,488,355,327 and 140,737,488,355,327.", ex0.Message);
+                var ex1 = Assert.Throws<ArgumentOutOfRangeException>(() => new IndirectReference(-140737488355328, 0));
+                Assert.StartsWith("Object number must be between -140,737,488,355,327 and 140,737,488,355,327.", ex1.Message);
 
-            var reference9 = new IndirectReference(-140737488355327, ushort.MaxValue + 10);
-            Assert.Equal(-140737488355327, reference9.ObjectNumber);
+                var ex2 = Assert.Throws<ArgumentOutOfRangeException>(() => new IndirectReference(1574, -1));
+                Assert.StartsWith("Generation number must not be a negative value.", ex2.Message);
 
-            var reference10 = new IndirectReference(140737488355327, ushort.MaxValue * 10);
-            Assert.Equal(140737488355327, reference10.ObjectNumber);
+                // We make sure object number is still correct even if generation is not
+                var reference6 = new IndirectReference(1574, int.MaxValue);
+                Assert.Equal(1574, reference6.ObjectNumber);
+
+                var reference7 = new IndirectReference(-1574, ushort.MaxValue + 10);
+                Assert.Equal(-1574, reference7.ObjectNumber);
+
+                var reference9 = new IndirectReference(-140737488355327, ushort.MaxValue + 10);
+                Assert.Equal(-140737488355327, reference9.ObjectNumber);
+
+                var reference10 = new IndirectReference(140737488355327, ushort.MaxValue * 10);
+                Assert.Equal(140737488355327, reference10.ObjectNumber);
+            }
+            finally
+            {
+                CultureInfo.CurrentCulture = lastCulture;
+            }
         }
 
         [Fact]

src/UglyToad.PdfPig.Tests/Dla/DlaHelper.cs

@@ -2,16 +2,23 @@
 {
     internal static class DlaHelper
     {
+        private static readonly string DlaFolder = Path.GetFullPath(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "..", "..", "..", "Dla", "Documents"));
+        private static readonly string IntegrationFolder = Path.GetFullPath(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "..", "..", "..", "Integration", "Documents"));
+
         public static string GetDocumentPath(string name, bool isPdf = true)
         {
-            var documentFolder = Path.GetFullPath(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "..", "..", "..", "Dla", "Documents"));
-
             if (!name.EndsWith(".pdf") && isPdf)
             {
                 name += ".pdf";
             }
 
-            return Path.Combine(documentFolder, name);
+            string doc = Path.Combine(DlaFolder, name);
+            if (File.Exists(doc))
+            {
+                return doc;
+            }
+            
+            return Path.Combine(IntegrationFolder, name);
         }
     }
 }

src/UglyToad.PdfPig.Tests/Dla/NearestNeighbourWordExtractorTests.cs

@@ -4,19 +4,84 @@
 
     public class NearestNeighbourWordExtractorTests
     {
-        [Fact]
-        public void Words2559Doc()
+        public static IEnumerable<object[]> DataWords => new[]
         {
-            // Microsoft Word count of words = 2559
+            new object[]
+            {
+                "2559 words.pdf",
+                5118,
+                2559
+            },
+            new object[]
+            {
+                "fseprd1102849.pdf",
+                12903,
+                11177
+            },
+            new object[]
+            {
+                "90 180 270 rotated.pdf",
+                589,
+                292
+            },
+            new object[]
+            {
+                "complex rotated.pdf",
+                805,
+                403
+            },
+            new object[]
+            {
+                "no horizontal distance.pdf",
+                4,
+                2
+            },
+            new object[]
+            {
+                "no vertical distance.pdf",
+                22,
+                10
+            },
+            new object[]
+            {
+                "no vertical horizontal distance.pdf",
+                4,
+                2
+            },
+            new object[]
+            {
+                "Random 2 Columns Lists Hyph - Justified.pdf",
+                1191,
+                607
+            },
+            new object[]
+            {
+                "caly-issues-56-1.pdf",
+                184,
+                156
+            },
+            new object[]
+            {
+                "caly-issues-58-2.pdf",
+                49,
+                49
+            },
+        };
 
-            using (var document = PdfDocument.Open(DlaHelper.GetDocumentPath("2559 words.pdf")))
+        [SkippableTheory]
+        [MemberData(nameof(DataWords))]
+        public void WordCount(string path, int wordCount, int noSpacesWordCount)
+        {
+            using (var document = PdfDocument.Open(DlaHelper.GetDocumentPath(path)))
             {
                 var page = document.GetPage(1);
                 var words = NearestNeighbourWordExtractor.Instance.GetWords(page.Letters).ToArray();
 
+                Assert.Equal(wordCount, words.Length);
+
                 var noSpacesWords = words.Where(x => !string.IsNullOrEmpty(x.Text.Trim())).ToArray();
 
-                Assert.Equal(2559, noSpacesWords.Length);
+                Assert.Equal(noSpacesWordCount, noSpacesWords.Length);
             }
         }
     }

src/UglyToad.PdfPig.Tests/Dla/UnsupervisedReadingOrderTests.cs

@@ -1,14 +1,12 @@
 namespace UglyToad.PdfPig.Tests.Dla
 {
-    using System;
+    using PdfFonts;
     using System.Collections.Generic;
     using System.Linq;
-    using System.Text;
-    using System.Threading.Tasks;
     using UglyToad.PdfPig.Content;
+    using UglyToad.PdfPig.Core;
     using UglyToad.PdfPig.DocumentLayoutAnalysis;
     using UglyToad.PdfPig.DocumentLayoutAnalysis.ReadingOrderDetector;
-    using UglyToad.PdfPig.Core;
 
     public class UnsupervisedReadingOrderTests
     {
@@ -62,10 +60,11 @@
         private static TextBlock CreateFakeTextBlock(PdfRectangle boundingBox)
         {
             var letter = new Letter("a",
+                boundingBox,
                 boundingBox,
                 boundingBox.BottomLeft,
                 boundingBox.BottomRight,
-                10, 1, null, TextRenderingMode.NeitherClip, null, null, 0, 0);// These don't matter
+                10, 1, (FontDetails)null, TextRenderingMode.NeitherClip, null, null, 0, 0);// These don't matter
             var leftTextBlock = new TextBlock(new[] { new TextLine(new[] { new Word(new[] { letter }) }) });
             return leftTextBlock;
         }

src/UglyToad.PdfPig.Tests/Fonts/SystemFonts/Linux.cs

@@ -4,6 +4,7 @@ using UglyToad.PdfPig.Tests.Dla;
 namespace UglyToad.PdfPig.Tests.Fonts.SystemFonts
 {
     using PdfPig.Core;
+    using PdfPig.Geometry;
 
     public class Linux
     {
@@ -68,7 +69,10 @@ namespace UglyToad.PdfPig.Tests.Fonts.SystemFonts
                     Assert.Equal(expectedData.TopLeft.Y, current.GlyphRectangle.TopLeft.Y, 6);
                     Assert.Equal(expectedData.Width, current.GlyphRectangle.Width, 6);
                     Assert.Equal(expectedData.Height, current.GlyphRectangle.Height, 6);
-                    Assert.Equal(expectedData.Rotation, current.GlyphRectangle.Rotation, 3);
+                    Assert.Equal(expectedData.Rotation, current.GlyphRectangle.Rotation, 3);
+                    
+                    Assert.True(current.GlyphRectangle.IntersectsWith(current.GlyphRectangleLoose));
+                    Assert.Equal(current.GlyphRectangle.Rotation, current.GlyphRectangleLoose.Rotation, 3);
                 }
             }
         }

src/UglyToad.PdfPig.Tests/Fonts/TrueType/Parser/TrueTypeFontParserTests.cs

@@ -229,5 +229,19 @@ namespace UglyToad.PdfPig.Tests.Fonts.TrueType.Parser
             Assert.NotNull(font.TableRegister.NameTable);
             Assert.NotEmpty(font.TableRegister.NameTable.NameRecords);
         }
+
+        [Fact]
+        public void Parse12623CorruptFileAndGetGlyphs()
+        {
+            var bytes = TrueTypeTestHelper.GetFileBytes("corrupt-12623");
+
+            var input = new TrueTypeDataBytes(new MemoryInputBytes(bytes));
+
+            var font = TrueTypeFontParser.Parse(input);
+
+            Assert.NotNull(font);
+
+            font.TryGetPath(1, out _);
+        }
     }
 }

src/UglyToad.PdfPig.Tests/Integration/CrossReferenceParserTests.cs

@@ -9,5 +9,17 @@
             using var document = PdfDocument.Open(path);
             Assert.Equal(3, document.NumberOfPages);
         }
+
+        [Fact]
+        public void CanReadDocumentWithCircularXRef()
+        {
+            string path = IntegrationHelpers.GetSpecificTestDocumentPath("B17-2000-transportation-fuels.pdf");
+
+            // If parser can't deal with xrefs that have circular references then
+            // opening the document will loop forever
+            using var document = PdfDocument.Open(path);
+
+            Assert.Equal(1, document.NumberOfPages);
+        }
     }
 }

src/UglyToad.PdfPig.Tests/Integration/FontDescriptorTests.cs

@@ -86,8 +86,8 @@
                     var letter = page.Letters[l];
                     var expected = DataBoldItalic[l];
                     Assert.Equal((string)expected[0], letter.Value);
-                    Assert.Equal((bool)expected[1], letter.Font.IsBold);
-                    Assert.Equal((bool)expected[2], letter.Font.IsItalic);
+                    Assert.Equal((bool)expected[1], letter.FontDetails.IsBold);
+                    Assert.Equal((bool)expected[2], letter.FontDetails.IsItalic);
                 }
             }
         }

src/UglyToad.PdfPig.Tests/Integration/GithubIssuesTests.cs

@@ -4,9 +4,76 @@
     using DocumentLayoutAnalysis.PageSegmenter;
     using DocumentLayoutAnalysis.WordExtractor;
     using PdfPig.Core;
+    using SkiaSharp;
 
     public class GithubIssuesTests
     {
+        [Fact]
+        public void Issue1183()
+        {
+            var path = IntegrationHelpers.GetDocumentPath("test_a.pdf");
+
+            byte[] expected =
+            [
+                82, 85, 134, 255, 87, 90, 139, 255, 81, 84, 133, 255, 87, 89, 139, 255, 89, 91, 141, 255, 81, 83, 133,
+                255, 84, 86, 136, 255, 84, 86, 136, 255, 70, 59, 113, 255, 69, 62, 116, 255, 75, 73, 126, 255, 45, 48,
+                100, 255, 42, 48, 99, 255, 50, 55, 107, 255, 56, 59, 111, 255, 64, 66, 118, 255, 68, 63, 118, 255, 61,
+                56, 111, 255, 70, 64, 120, 255, 67, 62, 117, 255, 61, 56, 111, 255, 68, 63, 118, 255, 68, 62, 118, 255,
+                59, 54, 109, 255, 61, 60, 117, 255, 69, 65, 122, 255, 67, 59, 116, 255, 71, 62, 118, 255, 66, 60, 115,
+                255, 47, 49, 102, 255, 40, 51, 102, 255, 35, 51, 100, 255, 70, 58, 114, 255, 68, 56, 112, 255, 76, 65,
+                121, 255, 68, 58, 114, 255, 66, 58, 114, 255, 71, 64, 119, 255, 62, 56, 111, 255, 67, 62, 117, 255, 77,
+                61, 118, 255, 71, 56, 113, 255, 76, 63, 119, 255, 74, 63, 118, 255, 63, 55, 108, 255, 71, 64, 116, 255,
+                73, 68, 119, 255, 52, 49, 99, 255, 38, 51, 99, 255, 49, 62, 110, 255, 39, 51, 100, 255, 46, 55, 106,
+                255, 50, 55, 107, 255, 63, 62, 116, 255, 67, 60, 116, 255, 71, 60, 116, 255, 67, 58, 112, 255, 68, 61,
+                114, 255, 70, 67, 119, 255, 50, 50, 101, 255, 42, 47, 96, 255, 49, 59, 106, 255, 40, 54, 100, 255, 42,
+                57, 103, 255, 51, 51, 102, 255, 67, 60, 112, 255, 73, 62, 114, 255, 71, 65, 117, 255, 48, 53, 103, 255,
+                45, 55, 104, 255, 49, 55, 105, 255, 63, 63, 114, 255, 68, 59, 115, 255, 71, 59, 115, 255, 73, 59, 115,
+                255, 74, 61, 118, 255, 66, 58, 114, 255, 50, 51, 105, 255, 39, 51, 104, 255, 34, 52, 103, 255, 64, 60,
+                116, 255, 67, 64, 119, 255, 66, 66, 120, 255, 46, 49, 102, 255, 45, 51, 102, 255, 52, 61, 111, 255, 39,
+                51, 99, 255, 41, 54, 102, 255, 42, 54, 100, 255, 43, 53, 99, 255, 47, 55, 103, 255, 51, 56, 104, 255,
+                56, 57, 108, 255, 67, 65, 117, 255, 67, 63, 116, 255, 52, 47, 100, 255, 44, 55, 106, 255, 44, 56, 106,
+                255, 42, 54, 103, 255, 42, 54, 102, 255, 40, 52, 100, 255, 41, 52, 99, 255, 45, 57, 103, 255, 42, 53,
+                99, 255, 38, 54, 95, 255, 39, 55, 97, 255, 47, 64, 105, 255, 37, 53, 95, 255, 37, 53, 95, 255, 46, 63,
+                104, 255, 39, 55, 96, 255, 42, 58, 99, 255, 41, 55, 105, 255, 45, 55, 106, 255, 46, 51, 103, 255, 51,
+                51, 103, 255, 63, 61, 114, 255, 70, 68, 121, 255, 60, 60, 113, 255, 46, 48, 100, 255, 49, 51, 101, 255,
+                51, 52, 103, 255, 58, 58, 109, 255, 69, 66, 119, 255, 64, 60, 113, 255, 61, 55, 109, 255, 70, 62, 118,
+                255, 67, 58, 114, 255, 72, 59, 115, 255, 70, 58, 115, 255, 72, 62, 118, 255, 61, 55, 110, 255, 64, 62,
+                116, 255, 65, 65, 119, 255, 47, 50, 104, 255, 52, 56, 109, 255, 39, 53, 106, 255, 41, 54, 107, 255, 40,
+                50, 102, 255, 45, 51, 103, 255, 64, 66, 117, 255, 62, 61, 112, 255, 67, 63, 114, 255, 53, 47, 98, 255,
+                49, 54, 101, 255, 51, 56, 104, 255, 43, 48, 95, 255, 50, 55, 102, 255, 49, 54, 102, 255, 42, 47, 94,
+                255, 51, 56, 103, 255, 47, 52, 100, 255, 72, 62, 114, 255, 71, 62, 114, 255, 72, 67, 119, 255, 52, 52,
+                103, 255, 44, 48, 99, 255, 48, 57, 106, 255, 39, 52, 100, 255, 43, 58, 106, 255, 43, 51, 98, 255, 44,
+                52, 99, 255, 48, 57, 104, 255, 46, 55, 102, 255, 41, 50, 97, 255, 45, 55, 101, 255, 49, 59, 105, 255,
+                43, 53, 100, 255, 51, 57, 106, 255, 41, 49, 98, 255, 40, 52, 100, 255, 45, 60, 107, 255, 38, 53, 101,
+                255, 36, 48, 96, 255, 46, 54, 102, 255, 49, 55, 104, 255, 44, 55, 104, 255, 46, 56, 105, 255, 48, 58,
+                107, 255, 41, 49, 99, 255, 43, 50, 100, 255, 52, 59, 108, 255, 50, 55, 105, 255, 50, 55, 105, 255, 43,
+                54, 105, 255, 42, 51, 102, 255, 45, 53, 104, 255, 45, 49, 101, 255, 63, 63, 116, 255, 66, 63, 116, 255,
+                68, 63, 117, 255, 62, 55, 109, 255, 74, 60, 120, 255, 73, 59, 119, 255, 72, 58, 119, 255, 76, 62, 122,
+                255, 74, 60, 120, 255, 71, 57, 118, 255, 75, 61, 121, 255, 76, 62, 123, 255
+            ];
+
+            using (var document = PdfDocument.Open(path, new ParsingOptions() { UseLenientParsing = true }))
+            {
+                var page = document.GetPage(16);
+                var images = page.GetImages().ToArray();
+                
+                Assert.Single(images);
+
+                var image = images[0];
+                
+                Assert.True(image.TryGetPng(out var bytes));
+
+                File.WriteAllBytes("test_a_16.png", bytes);
+
+                using (SKBitmap actual = SKBitmap.Decode(bytes, new SKImageInfo(431, 690, SKColorType.Bgra8888)))
+                {
+                    var pixels = actual.GetPixelSpan();
+                    Assert.Equal(1189560, pixels.Length);
+                    Assert.Equal(expected, pixels.Slice(0, 4 * 200).ToArray());
+                }
+            }
+        }
+
         [Fact]
         public void Issue1156()
         {
@@ -65,7 +132,7 @@
             var path = IntegrationHelpers.GetSpecificTestDocumentPath("StackOverflow_Issue_1122.pdf");
             
             var ex = Assert.Throws<PdfDocumentFormatException>(() => PdfDocument.Open(path, new ParsingOptions() { UseLenientParsing = true }));
-            Assert.StartsWith("Reached maximum search depth while getting indirect reference.", ex.Message);
+            Assert.Equal("The root object in the trailer did not resolve to a readable dictionary.", ex.Message);
         }
 
         [Fact]
@@ -124,7 +191,7 @@
         {
             var path = IntegrationHelpers.GetSpecificTestDocumentPath("SpookyPass.pdf");
             var ex = Assert.Throws<PdfDocumentFormatException>(() => PdfDocument.Open(path, new ParsingOptions() { UseLenientParsing = true }));
-            Assert.Equal("Avoiding infinite recursion in ObjectLocationProvider.TryGetOffset() as 'offset' and 'reference.ObjectNumber' have the same value and opposite signs.", ex.Message);
+            Assert.Equal("The root object in the trailer did not resolve to a readable dictionary.", ex.Message);
         }
 
         [Fact]
@@ -289,7 +356,8 @@
             using (var document = PdfDocument.Open(path, new ParsingOptions() { UseLenientParsing = true, SkipMissingFonts = true }))
             {
                 var page = document.GetPage(13);
-                Assert.Throws<OverflowException>(() => DocstrumBoundingBoxes.Instance.GetBlocks(page.GetWords()));
+                // This used to fail with an overflow exception when we failed to validate the zlib encoded data
+                Assert.NotNull(DocstrumBoundingBoxes.Instance.GetBlocks(page.GetWords()));
             }
         }
 
@@ -472,19 +540,13 @@
         {
             var doc = IntegrationHelpers.GetDocumentPath("ErcotFacts.pdf");
 
-            using (var document = PdfDocument.Open(doc, new ParsingOptions() { UseLenientParsing = true, SkipMissingFonts = true }))
-            {
-                var page1 = document.GetPage(1);
-                Assert.Equal(1788, page1.Letters.Count);
-
-                var page2 = document.GetPage(2);
-                Assert.Equal(2430, page2.Letters.Count);
-            }
-
             using (var document = PdfDocument.Open(doc, new ParsingOptions() { UseLenientParsing = true, SkipMissingFonts = false }))
             {
-                var ex = Assert.Throws<ArgumentNullException>(() => document.GetPage(1));
-                Assert.StartsWith("Value cannot be null.", ex.Message);
+                var page1 = document.GetPage(1);
+                Assert.Equal(1939, page1.Letters.Count);
+
+                var page2 = document.GetPage(2);
+                Assert.Equal(2434, page2.Letters.Count);
             }
         }
 

src/UglyToad.PdfPig.Tests/Integration/IntegrationDocumentTests.cs

@@ -1,5 +1,7 @@
 namespace UglyToad.PdfPig.Tests.Integration
 {
+    using PdfPig.Geometry;
+
     public class IntegrationDocumentTests
     {
         private static readonly Lazy<string> DocumentFolder = new Lazy<string>(() => Path.GetFullPath(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "..", "..", "..", "Integration", "Documents")));
@@ -11,6 +13,36 @@
             "cmap-parsing-exception.pdf"
         ];
 
+
+        [Theory]
+        [MemberData(nameof(GetAllDocuments))]
+        public void CheckGlyphLooseBoundingBoxes(string documentName)
+        {
+            // Add the full path back on, we removed it so we could see it in the test explorer.
+            documentName = Path.Combine(DocumentFolder.Value, documentName);
+
+            using (var document = PdfDocument.Open(documentName, new ParsingOptions { UseLenientParsing = true }))
+            {
+                for (var i = 0; i < document.NumberOfPages; i++)
+                {
+                    var page = document.GetPage(i + 1);
+                    foreach (var letter in page.Letters)
+                    {
+                        var bbox = letter.GlyphRectangle;
+                        if (bbox.Height > 0)
+                        {
+                            if (letter.GlyphRectangleLoose.Height <= 0)
+                            {
+                                _ = letter.GetFont().GetAscent();
+                            }
+                            
+                            Assert.True(letter.GlyphRectangleLoose.Height > 0, $"Page {i + 1}");
+                        }
+                    }
+                }
+            }
+        }
+
         [Theory]
         [MemberData(nameof(GetAllDocuments))]
         public void CanReadAllPages(string documentName)

src/UglyToad.PdfPig.Tests/Integration/Type0FontTests.cs

@@ -53,6 +53,8 @@ namespace UglyToad.PdfPig.Tests.Integration
 
                 Assert.Contains(page.Letters, x => x.GlyphRectangle.Width != 0);
                 Assert.Contains(page.Letters, x => x.GlyphRectangle.Height != 0);
+                Assert.Contains(page.Letters, x => x.GlyphRectangleLoose.Width != 0);
+                Assert.Contains(page.Letters, x => x.GlyphRectangleLoose.Height != 0);
             }
         }
     }

src/UglyToad.PdfPig.Tests/Integration/VisualVerification/GenerateLetterBoundingBoxImages.cs

@@ -147,6 +147,13 @@
             Run(Type3FontZeroHeight, 1255);
         }
 
+        [Fact]
+        public void test_a()
+        {
+            // Rendered glyphs are not correct, but we use the grid to assess
+            Run("test_a", 1584, 1);
+        }
+
         private static void Run(string file, int imageHeight = 792, int pageNo = 1)
         {
             var pdfFileName = GetFilename(file);
@@ -193,6 +200,32 @@
                         d.SaveTo(fs);
                     }
                 }
+
+                using (var bitmap = SKBitmap.FromImage(image))
+                using (var graphics = new SKCanvas(bitmap))
+                {
+                    foreach (var letter in page.Letters)
+                    {
+                        DrawRectangle(letter.GlyphRectangleLoose, graphics, violetPen, imageHeight, scale);
+                    }
+
+                    graphics.Flush();
+
+                    var imageName = $"{file}_loose.jpg";
+
+                    if (!Directory.Exists(OutputPath))
+                    {
+                        Directory.CreateDirectory(OutputPath);
+                    }
+
+                    var savePath = Path.Combine(OutputPath, imageName);
+
+                    using (var fs = new FileStream(savePath, FileMode.Create))
+                    using (SKData d = bitmap.Encode(SKEncodedImageFormat.Jpeg, 100))
+                    {
+                        d.SaveTo(fs);
+                    }
+                }
             }
         }
 
@@ -220,7 +253,11 @@
 
             pdf = pdf.Replace(".pdf", ".jpg");
 
-            return SKImage.FromEncodedData(pdf);
+            if (File.Exists(pdf))
+            {
+                return SKImage.FromEncodedData(pdf);
+            }
+            return SKImage.FromEncodedData(pdf.Replace(".jpg", ".png"));
         }
     }
 }

src/UglyToad.PdfPig.Tests/Integration/VisualVerification/GenerateLetterGlyphImages.cs

@@ -85,6 +85,31 @@
                         d.SaveTo(fs);
                     }
                 }
+
+                using (var picture = document.GetPage<SKPicture>(pageNo))
+                using (var image = SKImage.FromPicture(picture, size, ScaleMatrix))
+                using (var bmp = SKBitmap.FromImage(image))
+                using (var canvas = new SKCanvas(bmp))
+                {
+                    Assert.NotNull(picture);
+
+                    if (RenderGlyphRectangle)
+                    {
+                        foreach (var letter in page.Letters)
+                        {
+                            DrawRectangle(letter.GlyphRectangleLoose, canvas, redPaint, size.Height, Scale);
+                        }
+                    }
+
+                    var imageName = $"{file}_{pageNo}_loose.png";
+                    var savePath = Path.Combine(OutputPath, imageName);
+
+                    using (var fs = new FileStream(savePath, FileMode.Create))
+                    using (var d = bmp.Encode(SKEncodedImageFormat.Png, 100))
+                    {
+                        d.SaveTo(fs);
+                    }
+                }
             }
         }
 

src/UglyToad.PdfPig.Tests/Parser/FileStructure/FirstPassParserTests.cs

@@ -109,10 +109,8 @@ public class FirstPassParserTests
             %%EOF
             """;
 
-        if (Environment.NewLine == "\n")
-        {
-            content = content.Replace("\n", "\r\n");
-        }
+        // Handle "\r\n" or "\n" in the sourcecode in the same way
+        content = content.Replace("\r\n", "\n").Replace("\n", "\r\n");
 
         var ib = StringBytesTestConverter.Convert(content, false);
 

src/UglyToad.PdfPig.Tests/UglyToad.PdfPig.Tests.csproj

@@ -10,6 +10,7 @@
         <AssemblyOriginatorKeyFile>..\pdfpig.snk</AssemblyOriginatorKeyFile>
         <RuntimeFrameworkVersion Condition="'$(TargetFramework)'=='netcoreapp2.1'">2.1.30</RuntimeFrameworkVersion>
         <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>annotations</Nullable>
     </PropertyGroup>
 
     <ItemGroup>
@@ -39,11 +40,7 @@
     </ItemGroup>
 
     <ItemGroup>
-        <EmbeddedResource Remove="Fonts\TrueType\Andada-Regular.ttf" />
-        <EmbeddedResource Remove="Fonts\TrueType\google-simple-doc.ttf" />
-        <EmbeddedResource Remove="Fonts\TrueType\issue-258-corrupt-name-table.ttf" />
-        <EmbeddedResource Remove="Fonts\TrueType\PMingLiU.ttf" />
-        <EmbeddedResource Remove="Fonts\TrueType\Roboto-Regular.ttf" />
+        <EmbeddedResource Remove="Fonts\TrueType\*.ttf" />
         <EmbeddedResource Remove="Fonts\Type1\AdobeUtopia.pfa" />
         <EmbeddedResource Remove="Fonts\Type1\CMBX10.pfa" />
         <EmbeddedResource Remove="Fonts\Type1\CMBX12.pfa" />
@@ -61,24 +58,12 @@
         <Content Include="Fonts\CompactFontFormat\MinionPro.bin">
             <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
         </Content>
-        <Content Include="Fonts\TrueType\Andada-Regular.ttf">
-            <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-        </Content>
-        <Content Include="Fonts\TrueType\google-simple-doc.ttf">
-            <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-        </Content>
-        <Content Include="Fonts\TrueType\issue-258-corrupt-name-table.ttf">
-            <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-        </Content>
-        <Content Include="Fonts\TrueType\PMingLiU.ttf">
+        <Content Include="Fonts\TrueType\*.ttf">
             <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
         </Content>
         <Content Include="Fonts\TrueType\Roboto-Regular.GlyphData.txt">
             <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
         </Content>
-        <Content Include="Fonts\TrueType\Roboto-Regular.ttf">
-            <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-        </Content>
         <Content Include="Fonts\Type1\AdobeUtopia.pfa" />
         <Content Include="Fonts\Type1\CMBX10.pfa" />
         <Content Include="Fonts\Type1\CMBX12.pfa" />
@@ -117,9 +102,18 @@
         <None Update="Dla\Documents\90 180 270 rotated.pdf">
             <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
         </None>
+        <None Update="Dla\Documents\caly-issues-56-1.pdf">
+          <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+        </None>
+        <None Update="Dla\Documents\caly-issues-58-2.pdf">
+          <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+        </None>
         <None Update="Dla\Documents\complex rotated.pdf">
             <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
         </None>
+        <None Update="Dla\Documents\fseprd1102849.pdf">
+          <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+        </None>
         <None Update="Dla\Documents\no horizontal distance.pdf">
             <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
         </None>

src/UglyToad.PdfPig.Tests/Writer/PdfDocumentBuilderTests.cs

@@ -1154,7 +1154,7 @@
                         {
                             location += letter.Location.X;
                             location += letter.Location.Y;
-                            location += letter.Font.Name.Length;
+                            location += letter.FontDetails.Name.Length;
                         }
                     }
                 }

src/UglyToad.PdfPig/Content/Letter.cs

@@ -46,6 +46,12 @@
         /// </summary>
         public PdfRectangle GlyphRectangle { get; }
 
+        /// <summary>
+        /// The loose bounding box for the glyph. Contrary to the <see cref="GlyphRectangle"/>, the loose bounding box will be the same across all glyphes of the same font.
+        /// It takes in account the font Ascent and Descent.
+        /// </summary>
+        public PdfRectangle GlyphRectangleLoose { get; }
+
         /// <summary>
         /// Size as defined in the PDF file. This is not equivalent to font size in points but is relative to other font sizes on the page.
         /// </summary>
@@ -54,12 +60,20 @@
         /// <summary>
         /// The name of the font.
         /// </summary>
-        public string? FontName => Font?.Name;
+        public string? FontName => FontDetails?.Name;
 
         /// <summary>
         /// Details about the font for this letter.
         /// </summary>
-        public FontDetails Font { get; }
+        public FontDetails FontDetails { get; }
+
+        /// <summary>
+        /// Details about the font for this letter.
+        /// </summary>
+        [Obsolete("Use FontDetails instead.")]
+        public FontDetails Font => FontDetails;
+
+        private readonly IFont? _font;
 
         /// <summary>
         /// Text rendering mode that indicates whether we should draw this letter's strokes,
@@ -100,12 +114,58 @@
         /// <summary>
         /// Create a new letter to represent some text drawn by the Tj operator.
         /// </summary>
-        public Letter(string value, PdfRectangle glyphRectangle,
+        public Letter(string value,
+            PdfRectangle glyphRectangle,
+            PdfRectangle glyphRectangleLoose,
             PdfPoint startBaseLine,
             PdfPoint endBaseLine,
             double width,
             double fontSize,
-            FontDetails font,
+            IFont font,
+            TextRenderingMode renderingMode,
+            IColor strokeColor,
+            IColor fillColor,
+            double pointSize,
+            int textSequence) :
+                this(value, glyphRectangle, glyphRectangleLoose,
+                    startBaseLine, endBaseLine,
+                    width, fontSize, font.Details, font,
+                    renderingMode, strokeColor, fillColor,
+                    pointSize, textSequence)
+        { }
+
+        /// <summary>
+        /// Create a new letter to represent some text drawn by the Tj operator.
+        /// </summary>
+        public Letter(string value,
+            PdfRectangle glyphRectangle,
+            PdfRectangle glyphRectangleLoose,
+            PdfPoint startBaseLine,
+            PdfPoint endBaseLine,
+            double width,
+            double fontSize,
+            FontDetails fontDetails,
+            TextRenderingMode renderingMode,
+            IColor strokeColor,
+            IColor fillColor,
+            double pointSize,
+            int textSequence): 
+                this(value, glyphRectangle, glyphRectangleLoose,
+                    startBaseLine, endBaseLine,
+                    width, fontSize, fontDetails, null,
+                    renderingMode, strokeColor, fillColor,
+                    pointSize, textSequence)
+        { }
+
+        private Letter(string value,
+            PdfRectangle glyphRectangle,
+            PdfRectangle glyphRectangleLoose,
+            PdfPoint startBaseLine,
+            PdfPoint endBaseLine,
+            double width,
+            double fontSize,
+            FontDetails fontDetails,
+            IFont? font,
             TextRenderingMode renderingMode,
             IColor strokeColor,
             IColor fillColor,
@@ -114,11 +174,13 @@
         {
             Value = value;
             GlyphRectangle = glyphRectangle;
+            GlyphRectangleLoose = glyphRectangleLoose;
             StartBaseLine = startBaseLine;
             EndBaseLine = endBaseLine;
             Width = width;
             FontSize = fontSize;
-            Font = font;
+            FontDetails = fontDetails;
+            _font = font;
             RenderingMode = renderingMode;
             if (renderingMode == TextRenderingMode.Stroke)
             {
@@ -135,6 +197,43 @@
             TextOrientation = GetTextOrientation();
         }
 
+        /// <summary>
+        /// Creates a new <see cref="Letter"/> instance with the same properties as the current instance,
+        /// but with the font details set to bold.
+        /// </summary>
+        /// <returns>
+        /// A new <see cref="Letter"/> instance with bold font details.
+        /// </returns>
+        public Letter AsBold()
+        {
+            return new Letter(Value,
+                GlyphRectangle,
+                GlyphRectangleLoose,
+                StartBaseLine,
+                EndBaseLine,
+                Width,
+                FontSize,
+                FontDetails.AsBold(),
+                _font,
+                RenderingMode,
+                StrokeColor,
+                FillColor,
+                PointSize,
+                TextSequence);
+        }
+
+        /// <summary>
+        /// Retrieves the font associated with this letter, if available.
+        /// </summary>
+        /// <returns>
+        /// The <see cref="IFont"/> instance representing the font used for this letter, 
+        /// or <c>null</c> if no font is associated.
+        /// </returns>
+        public IFont? GetFont()
+        {
+            return _font;
+        }
+        
         private TextOrientation GetTextOrientation()
         {
             if (Math.Abs(StartBaseLine.Y - EndBaseLine.Y) < 10e-5)

src/UglyToad.PdfPig/Content/Pages.cs

@@ -182,16 +182,15 @@
 
         public void Dispose()
         {
-            foreach (var key in pageFactoryCache.Keys)
+            foreach (var factory in pageFactoryCache.Values)
             {
-                var factory = pageFactoryCache[key];
-                pageFactoryCache.Remove(key);
-
                 if (factory is IDisposable disposable)
                 {
                     disposable.Dispose();
                 }
             }
+
+            pageFactoryCache.Clear();
         }
     }
 }

src/UglyToad.PdfPig/CrossReference/CrossReferenceTableBuilder.cs

@@ -56,16 +56,16 @@
                 // add this and follow chain defined by 'Prev' keys
                 xrefPartToBytePositionOrder.Add(firstCrossReferenceOffset);
 
-                // Get any streams that are tied to this table.
-                var activePart = currentPart;
-                var dependents = parts.Where(x => x.TiedToXrefAtOffset == activePart.Offset);
-                foreach (var dependent in dependents)
-                {
-                    xrefPartToBytePositionOrder.Add(dependent.Offset);
-                }
-
                 while (currentPart.Dictionary != null)
                 {
+                    // Get any streams that are tied to this table.
+                    var activePart = currentPart;
+                    var dependents = parts.Where(x => x.TiedToXrefAtOffset == activePart.Offset);
+                    foreach (var dependent in dependents)
+                    {
+                        xrefPartToBytePositionOrder.Add(dependent.Offset);
+                    }
+
                     long prevBytePos = currentPart.GetPreviousOffset();
                     if (prevBytePos == -1)
                     {

src/UglyToad.PdfPig/Filters/Adler32ChecksumStream.cs

@@ -0,0 +1,82 @@
+namespace UglyToad.PdfPig.Filters
+{
+    using System;
+    using System.IO;
+
+    internal sealed class Adler32ChecksumStream : Stream
+    {
+        private readonly Stream underlyingStream;
+
+        public Adler32ChecksumStream(Stream writeStream)
+        {
+            underlyingStream = writeStream ?? throw new ArgumentNullException(nameof(writeStream));
+        }
+        public override bool CanRead => underlyingStream.CanRead;
+
+        public override bool CanSeek => false;
+
+        public override bool CanWrite => underlyingStream.CanWrite;
+
+        public override long Length => underlyingStream.Length;
+
+        public override long Position { get => underlyingStream.Position; set => throw new NotImplementedException(); }
+
+        public override void Flush()
+        {
+            underlyingStream.Flush();
+        }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            int n = underlyingStream.Read(buffer, offset, count);
+
+            if (n > 0)
+            {
+                UpdateAdler(buffer.AsSpan(offset, n));
+            }
+            return n;
+        }
+
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            throw new InvalidOperationException();
+        }
+
+        public override void SetLength(long value)
+        {
+            throw new InvalidOperationException();
+        }
+
+        public override void Write(byte[] buffer, int offset, int count)
+        {
+            underlyingStream.Write(buffer, offset, count);
+
+            if (count > 0)
+            {
+                UpdateAdler(buffer.AsSpan(offset, count));
+            }
+        }
+
+        public uint Checksum { get; private set; } = 1;
+
+        private void UpdateAdler(Span<byte> span)
+        {
+            const uint MOD_ADLER = 65521;
+            uint a = Checksum & 0xFFFF;
+            uint b = (Checksum >> 16) & 0xFFFF;
+
+            foreach (byte c in span)
+            {
+                a = (a + c) % MOD_ADLER;
+                b = (b + a) % MOD_ADLER;
+            }
+
+            Checksum = (b << 16) | a;
+        }
+
+        public override void Close()
+        {
+            underlyingStream.Close();
+        }
+    }
+}

src/UglyToad.PdfPig/Filters/FlateFilter.cs

@@ -2,6 +2,7 @@
 {
     using Fonts;
     using System;
+    using System.Buffers.Binary;
     using System.IO;
     using System.IO.Compression;
     using Tokens;
@@ -43,6 +44,15 @@
                 var colors = Math.Min(parameters.GetIntOrDefault(NameToken.Colors, DefaultColors), 32);
                 var bitsPerComponent = parameters.GetIntOrDefault(NameToken.BitsPerComponent, DefaultBitsPerComponent);
                 var columns = parameters.GetIntOrDefault(NameToken.Columns, DefaultColumns);
+
+                var length = parameters.GetIntOrDefault(NameToken.Length, -1);
+
+                if (length > 0 && length < input.Length)
+                {
+                    // Truncates final "\r\n" or "\n" from source data if any. Fixes detecting where the adler checksum is. (Zlib uses framing for this)
+                    input = input.Slice(0, length);
+                }
+
                 return Decompress(input, predictor, colors, bitsPerComponent, columns);
             }
             catch
@@ -55,29 +65,83 @@
 
         private static Memory<byte> Decompress(Memory<byte> input, int predictor, int colors, int bitsPerComponent, int columns)
         {
-            using (var memoryStream = MemoryHelper.AsReadOnlyMemoryStream(input))
+#if NET
+            using var memoryStream = MemoryHelper.AsReadOnlyMemoryStream(input);
+            try
             {
-                // The first 2 bytes are the header which DeflateStream does not support.
-                memoryStream.ReadByte();
-                memoryStream.ReadByte();
-
-                try
+                using (var zlib = new ZLibStream(memoryStream, CompressionMode.Decompress))
+                using (var output = new MemoryStream((int)(input.Length * 1.5)))
+                using (var f = PngPredictor.WrapPredictor(output, predictor, colors, bitsPerComponent, columns))
                 {
-                    using (var deflate = new DeflateStream(memoryStream, CompressionMode.Decompress))
-                    using (var output = new MemoryStream((int)(input.Length * 1.5)))
-                    using (var f = PngPredictor.WrapPredictor(output, predictor, colors, bitsPerComponent, columns))
-                    {
-                        deflate.CopyTo(f);
-                        f.Flush();
+                    zlib.CopyTo(f);
+                    f.Flush();
 
-                        return output.AsMemory();
-                    }
-                }
-                catch (InvalidDataException ex)
-                {
-                    throw new CorruptCompressedDataException("Invalid Flate compressed stream encountered", ex);
+                    return output.AsMemory();
                 }
             }
+            catch (InvalidDataException ex)
+            {
+                throw new CorruptCompressedDataException("Invalid Flate compressed stream encountered", ex);
+            }
+#else
+            // Ideally we would like to use the ZLibStream class but that is only available in .NET 5+.
+            // We look at the raw data now
+            // *  First we have 2 bytes, specifying the type of compression
+            // * Then we have the deflated data
+            // * Then we have a 4 byte checksum (Adler32)
+
+            // Would be so nice to have zlib do the framing here... but the deflate stream already reads data from the stream that we need.
+
+            using var memoryStream = MemoryHelper.AsReadOnlyMemoryStream(input.Slice(2, input.Length - 2 /* Header */ - 4 /* Checksum */));
+            // The first 2 bytes are the header which DeflateStream can't handle. After the s
+            var adlerBytes = input.Slice(input.Length - 4, 4).Span;
+            uint expected = BinaryPrimitives.ReadUInt32BigEndian(adlerBytes);
+            uint altExpected = expected;
+
+            // Sometimes the data ends with "\r\n", "\r" or "\n" and we don't know if it is part of the zlib
+            // Ideally this would have been removed by the caller from the provided length...
+            if (adlerBytes[3] == '\n' || adlerBytes[3] == '\r')
+            {
+                if (adlerBytes[3] == '\n' && adlerBytes[2] == '\r')
+                {
+                    // Now we don't know which value is the good one. The value could be ok, or padding.
+                    // Lets allow both values for now. Allowing two out of 2^32 is much better than allowing everything
+                    adlerBytes = input.Slice(input.Length - 6, 4).Span;
+                }
+                else
+                {
+                    // Same but now for just '\n' or '\r' instead of '\r\n'
+                    adlerBytes = input.Slice(input.Length - 5, 4).Span;
+                }
+
+                altExpected = BinaryPrimitives.ReadUInt32BigEndian(adlerBytes);
+            }
+
+
+            try
+            {
+                using (var deflate = new DeflateStream(memoryStream, CompressionMode.Decompress))
+                using (var adlerStream = new Adler32ChecksumStream(deflate))
+                using (var output = new MemoryStream((int)(input.Length * 1.5)))
+                using (var f = PngPredictor.WrapPredictor(output, predictor, colors, bitsPerComponent, columns))
+                {
+                    adlerStream.CopyTo(f);
+                    f.Flush();
+
+                    uint actual = adlerStream.Checksum;
+                    if (expected != actual && altExpected != actual)
+                    {
+                        throw new CorruptCompressedDataException("Flate stream has invalid checksum");
+                    }
+
+                    return output.AsMemory();
+                }
+            }
+            catch (InvalidDataException ex)
+            {
+                throw new CorruptCompressedDataException("Invalid Flate compressed stream encountered", ex);
+            }
+#endif
         }
 
         /// <inheritdoc />
@@ -95,9 +159,10 @@
 
             using (var compressStream = new MemoryStream())
             using (var compressor = new DeflateStream(compressStream, CompressionLevel.Fastest))
+            using (var adlerStream = new Adler32ChecksumStream(compressor))
             {
-                compressor.Write(data, 0, data.Length);
-                compressor.Close();
+                adlerStream.Write(data, 0, data.Length);
+                adlerStream.Close();
 
                 var compressed = compressStream.ToArray();
 
@@ -111,7 +176,7 @@
                 Array.Copy(compressed, 0, result, headerLength, compressed.Length);
 
                 // Write Checksum of raw data.
-                var checksum = Adler32Checksum.Calculate(data);
+                var checksum = adlerStream.Checksum;
 
                 var offset = headerLength + compressed.Length;
 

src/UglyToad.PdfPig/Graphics/ContentStreamProcessor.cs

@@ -100,12 +100,6 @@ namespace UglyToad.PdfPig.Graphics
             var transformedGlyphBounds = PerformantRectangleTransformer
                 .Transform(renderingMatrix, textMatrix, transformationMatrix, characterBoundingBox.GlyphBounds);
             
-            var transformedPdfBounds = PerformantRectangleTransformer
-                .Transform(renderingMatrix,
-                    textMatrix,
-                    transformationMatrix,
-                    new PdfRectangle(0, 0, characterBoundingBox.Width, UserSpaceUnit.PointMultiples));
-
             if (ParsingOptions.ClipPaths)
             {
                 var currentClipping = currentState.CurrentClippingPath;
@@ -129,11 +123,12 @@ namespace UglyToad.PdfPig.Graphics
                     letter = new Letter(
                         newLetter,
                         attachTo.GlyphRectangle,
+                        attachTo.GlyphRectangleLoose,
                         attachTo.StartBaseLine,
                         attachTo.EndBaseLine,
                         attachTo.Width,
                         attachTo.FontSize,
-                        attachTo.Font,
+                        attachTo.GetFont()!,
                         attachTo.RenderingMode,
                         attachTo.StrokeColor,
                         attachTo.FillColor,
@@ -151,14 +146,30 @@ namespace UglyToad.PdfPig.Graphics
             // If we did not create a letter for a combined diacritic, create one here.
             if (letter is null)
             {
+                var transformedPdfBounds = PerformantRectangleTransformer
+                    .Transform(renderingMatrix,
+                        textMatrix,
+                        transformationMatrix,
+                        new PdfRectangle(0, 0, characterBoundingBox.Width, UserSpaceUnit.PointMultiples));
+
+                var looseBox = PerformantRectangleTransformer
+                    .Transform(renderingMatrix,
+                        textMatrix,
+                        transformationMatrix,
+                        new PdfRectangle(0,
+                            font.GetDescent(),
+                            characterBoundingBox.Width,
+                            font.GetAscent()));
+
                 letter = new Letter(
                     unicode,
                     isBboxValid ? transformedGlyphBounds : transformedPdfBounds,
+                    looseBox,
                     transformedPdfBounds.BottomLeft,
                     transformedPdfBounds.BottomRight,
                     transformedPdfBounds.Width,
                     fontSize,
-                    font.Details,
+                    font,
                     currentState.FontState.TextRenderingMode,
                     currentState.CurrentStrokingColor!,
                     currentState.CurrentNonStrokingColor!,
@@ -167,7 +178,6 @@ namespace UglyToad.PdfPig.Graphics
             }
 
             letters.Add(letter);
-
             markedContentStack.AddLetter(letter);
         }
 

src/UglyToad.PdfPig/Images/ColorSpaceDetailsByteConverter.cs

@@ -39,7 +39,16 @@
             var strideWidth = decoded.Length / imageHeight / bytesPerPixel;
             if (strideWidth != imageWidth)
             {
-                decoded = RemoveStridePadding(decoded, strideWidth, imageWidth, imageHeight, bytesPerPixel);
+                if (bytesPerPixel > 1)
+                {
+                    // Fixed thanks to / see discussion at https://github.com/UglyToad/PdfPig/issues/1183
+                    // Unclear what should be done here, we assume we can just remove the trailing bytes
+                    decoded = decoded.Slice(0, imageWidth * imageHeight * bytesPerPixel);
+                }
+                else
+                {
+                    decoded = RemoveStridePadding(decoded, strideWidth, imageWidth, imageHeight, bytesPerPixel);
+                }
             }
 
             return details.Transform(decoded);

src/UglyToad.PdfPig/Images/Png/Adler32Checksum.cs

@@ -1,35 +0,0 @@
-namespace UglyToad.PdfPig.Images.Png
-{
-    using System;
-
-    /// <summary>
-    /// Used to calculate the Adler-32 checksum used for ZLIB data in accordance with 
-    /// RFC 1950: ZLIB Compressed Data Format Specification.
-    /// </summary>
-    internal static class Adler32Checksum
-    {
-        // Both sums (s1 and s2) are done modulo 65521.
-        private const int AdlerModulus = 65521;
-
-        /// <summary>
-        /// Calculate the Adler-32 checksum for some data.
-        /// </summary>
-        public static int Calculate(ReadOnlySpan<byte> data)
-        {
-            // s1 is the sum of all bytes.
-            var s1 = 1;
-
-            // s2 is the sum of all s1 values.
-            var s2 = 0;
-
-            foreach (var b in data)
-            {
-                s1 = (s1 + b) % AdlerModulus;
-                s2 = (s1 + s2) % AdlerModulus;
-            }
-
-            // The Adler-32 checksum is stored as s2*65536 + s1.
-            return s2 * 65536 + s1;
-        }
-    }
-}

src/UglyToad.PdfPig/Images/Png/PngBuilder.cs

@@ -1,8 +1,10 @@
 namespace UglyToad.PdfPig.Images.Png
 {
+    using System.Buffers.Binary;
     using System.IO;
     using System.IO.Compression;
     using System.Text;
+    using UglyToad.PdfPig.Filters;
 
     /// <summary>
     /// Used to construct PNG images. Call <see cref="Create"/> to make a new builder.
@@ -121,9 +123,10 @@
             const int checksumLength = 4;
             using (var compressStream = new MemoryStream())
             using (var compressor = new DeflateStream(compressStream, CompressionLevel.Fastest, true))
+            using (var adlerStream = new Adler32ChecksumStream(compressor))
             {
-                compressor.Write(data, 0, data.Length);
-                compressor.Close();
+                adlerStream.Write(data, 0, data.Length);
+                adlerStream.Close();
 
                 compressStream.Seek(0, SeekOrigin.Begin);
 
@@ -143,15 +146,11 @@
                 }
 
                 // Write Checksum of raw data.
-                var checksum = Adler32Checksum.Calculate(data);
+                var checksum = adlerStream.Checksum;
 
                 var offset = headerLength + compressStream.Length;
 
-                result[offset++] = (byte)(checksum >> 24);
-                result[offset++] = (byte)(checksum >> 16);
-                result[offset++] = (byte)(checksum >> 8);
-                result[offset] = (byte)(checksum >> 0);
-
+                BinaryPrimitives.WriteUInt32BigEndian(result.AsSpan((int)offset, 4), checksum);
                 return result;
             }
         }

src/UglyToad.PdfPig/Images/Png/PngFromPdfImageFactory.cs

@@ -1,11 +1,11 @@
-namespace UglyToad.PdfPig.Images.Png
+namespace UglyToad.PdfPig.Images.Png
 {
     using System.Diagnostics.CodeAnalysis;
-    using Content;
+    using Content;
     using Graphics.Colors;
     using UglyToad.PdfPig.Core;
 
-    internal static class PngFromPdfImageFactory
+    internal static class PngFromPdfImageFactory
     {
         private static bool TryGenerateSoftMask(IPdfImage image, [NotNullWhen(true)] out ReadOnlySpan<byte> maskBytes)
         {
@@ -26,9 +26,9 @@
                 return false;
             }
 
-            if (!mask.TryGetBytesAsMemory(out var maskMemory))
-            {
-                return false;
+            if (!mask.TryGetBytesAsMemory(out var maskMemory))
+            {
+                return false;
             }
 
             try
@@ -67,24 +67,24 @@
                     bytesPure[actualSize - 2] == ReadHelper.AsciiCarriageReturn &&
                     bytesPure[actualSize - 1] == ReadHelper.AsciiLineFeed);
         }
-
-        public static bool TryGenerate(IPdfImage image, [NotNullWhen(true)] out byte[]? bytes)
-        {
-            bytes = null;
-
-            var hasValidDetails = image.ColorSpaceDetails != null && !(image.ColorSpaceDetails is UnsupportedColorSpaceDetails);
-
+
+        public static bool TryGenerate(IPdfImage image, [NotNullWhen(true)] out byte[]? bytes)
+        {
+            bytes = null;
+
+            var hasValidDetails = image.ColorSpaceDetails != null && !(image.ColorSpaceDetails is UnsupportedColorSpaceDetails);
+
             var isColorSpaceSupported = hasValidDetails && image.ColorSpaceDetails!.BaseType != ColorSpace.Pattern;
-
-            if (!isColorSpaceSupported || !image.TryGetBytesAsMemory(out var imageMemory))
-            {
-                return false;
+
+            if (!isColorSpaceSupported || !image.TryGetBytesAsMemory(out var imageMemory))
+            {
+                return false;
             }
 
-            var bytesPure = imageMemory.Span;
-
-            try
-            {
+            var bytesPure = imageMemory.Span;
+
+            try
+            {
                 bytesPure = ColorSpaceDetailsByteConverter.Convert(image.ColorSpaceDetails!, bytesPure,
                     image.BitsPerComponent, image.WidthInSamples, image.HeightInSamples);
 
@@ -108,7 +108,7 @@
                     }
                 }
 
-                var builder = PngBuilder.Create(image.WidthInSamples, image.HeightInSamples, hasMask);
+                var builder = PngBuilder.Create(image.WidthInSamples, image.HeightInSamples, hasMask);
 
                 if (!IsCorrectlySized(image, bytesPure))
                 {
@@ -183,17 +183,17 @@
                             }
                         }
                     }
-                }
-
-                bytes = builder.Save();
-                return true;
-            }
-            catch
+                }
+
+                bytes = builder.Save();
+                return true;
+            }
+            catch
             {
-                // ignored.
-            }
-
-            return false;
+                // ignored.
+            }
+
+            return false;
         }
-    }
-}
+    }
+}

src/UglyToad.PdfPig/Parser/FileStructure/FileHeaderOffset.cs

@@ -4,14 +4,14 @@
 /// How many bytes precede the "%PDF-" version header in the file. In some files this 'junk' can
 /// offset all following offset bytes.
 /// </summary>
-internal readonly struct FileHeaderOffset(int value)
+internal readonly record struct FileHeaderOffset(int Value) : IEquatable<FileHeaderOffset>
 {
-    public int Value => value;
+    public override string ToString() => Value.ToString();
+    
+    public bool Equals(FileHeaderOffset other)
+    {
+        return Value == other.Value;
+    }
 
-    public override string ToString() => value.ToString();
-
-    public override bool Equals(object? obj) =>
-        obj is FileHeaderOffset other && value == other.Value;
-
-    public override int GetHashCode() => value.GetHashCode();
+    public override int GetHashCode() => Value.GetHashCode();
 }

src/UglyToad.PdfPig/Parser/FileStructure/FirstPassParser.cs

@@ -153,6 +153,23 @@ internal static partial class FirstPassParser
             {
                 results.Add(table);
                 nextLocation = table.GetPrevious();
+
+                // Also add any optional associated Stream
+                var xRefStm = table.GetXRefStm();
+                if (xRefStm is long xRefStmValue)
+                {
+                    var stream = GetXrefStreamOrTable(
+                        offset,
+                        input,
+                        scanner,
+                        xRefStmValue,
+                        log);
+
+                    if (stream != null)
+                    {
+                        results.Add(stream);
+                    }
+                }
             }
             else if (streamOrTable is XrefStream stream)
             {

src/UglyToad.PdfPig/Parser/FileStructure/XrefBruteForcer.cs

@@ -16,6 +16,9 @@ internal static class XrefBruteForcer
     {
         var results = new List<IXrefSection>();
 
+        // Guard against circular references; only read xref at each offset once
+        var xrefOffsetSeen = new HashSet<long>();
+
         var bruteForceObjPositions = new Dictionary<IndirectReference, long>();
 
         DictionaryToken? trailer = null;
@@ -131,6 +134,14 @@ internal static class XrefBruteForcer
                 ClearQueues();
 
                 var potentialTableOffset = bytes.CurrentOffset - 4;
+
+                if (xrefOffsetSeen.Contains(potentialTableOffset))
+                {
+                    log.Debug($"Skipping circular xref reference at {potentialTableOffset}");
+                    continue;
+                }
+                xrefOffsetSeen.Add(potentialTableOffset);
+
                 var table = XrefTableParser.TryReadTableAtOffset(
                     new FileHeaderOffset(0),
                     potentialTableOffset,
@@ -152,15 +163,22 @@ internal static class XrefBruteForcer
             {
                 ClearQueues();
 
-                if (!lastObjPosition.HasValue)
+                if (lastObjPosition is not long offset)
                 {
                     log.Error("Found an /XRef without having encountered an object first");
                     continue;
                 }
 
+                if (xrefOffsetSeen.Contains(offset))
+                {
+                    log.Debug($"Skipping circular /XRef reference at {offset}");
+                    continue;
+                }
+                xrefOffsetSeen.Add(offset);
+
                 var stream = XrefStreamParser.TryReadStreamAtOffset(
                     new FileHeaderOffset(0),
-                    lastObjPosition.Value,
+                    offset,
                     bytes,
                     scanner,
                     log);

src/UglyToad.PdfPig/Parser/FileStructure/XrefTable.cs

@@ -44,4 +44,14 @@ internal sealed class XrefTable : IXrefSection
 
         return null;
     }
+
+    public long? GetXRefStm()
+    {
+        if (Dictionary != null && Dictionary.TryGet(NameToken.XrefStm, out NumericToken xRefStm))
+        {
+            return xRefStm.Long;
+        }
+
+        return null;
+    }
 }

src/UglyToad.PdfPig/Parser/PdfDocumentFactory.cs

@@ -44,9 +44,23 @@
 
         internal static PdfDocument Open(Stream stream, ParsingOptions? options)
         {
-            var streamInput = new StreamInputBytes(stream, false);
-
-            var initialPosition = stream.Position;
+            StreamInputBytes streamInput;
+            long initialPosition;
+            
+            if (stream is { CanRead: true, CanSeek: false })
+            {
+                // We need the stream to be seekable
+                var ms = new MemoryStream();
+                stream.CopyTo(ms); // Copy the non seekable stream in memory (seekable)
+                ms.Position = 0;
+                streamInput = new StreamInputBytes(ms, true); // The created memory stream will be disposed on document dispose
+                initialPosition = ms.Position;
+            }
+            else
+            {
+                streamInput = new StreamInputBytes(stream, false);
+                initialPosition = stream.Position;
+            }
 
             try
             {
@@ -225,6 +239,11 @@
 
             var rootDictionary = DirectObjectFinder.Get<DictionaryToken>(trailer.Root, pdfTokenScanner)!;
 
+            if (rootDictionary is null)
+            {
+                throw new PdfDocumentFormatException($"The root object in the trailer did not resolve to a readable dictionary.");
+            }
+
             if (!rootDictionary.ContainsKey(NameToken.Type) && isLenientParsing)
             {
                 rootDictionary = rootDictionary.With(NameToken.Type, NameToken.Catalog);

src/UglyToad.PdfPig/PdfDocument.cs

@@ -112,10 +112,14 @@
 
         /// <summary>
         /// Creates a <see cref="PdfDocument"/> for reading from the provided stream.
+        /// <para>
+        /// If the stream provided is not seekable (<see cref="Stream.CanSeek"/> is <c>false</c>), the stream will be copied into a new <see cref="MemoryStream"/>.
+        /// </para>
         /// The caller must manage disposing the stream. The created PdfDocument will not dispose the stream.
         /// </summary>
         /// <param name="stream">
         /// A stream of the file contents, this must support reading and seeking.
+        /// <para>If the stream provided is not seekable (<see cref="Stream.CanSeek"/> is <c>false</c>), the stream will be copied into a new <see cref="MemoryStream"/>.</para>
         /// The PdfDocument will not dispose of the provided stream.
         /// </param>
         /// <param name="options">Optional parameters controlling parsing.</param>

src/UglyToad.PdfPig/PdfExtensions.cs

@@ -7,6 +7,7 @@
     using Parser.Parts;
     using Tokenization.Scanner;
     using Tokens;
+    using UglyToad.PdfPig.Util;
 
     /// <summary>
     /// Extensions for PDF types.
@@ -62,6 +63,18 @@
             double totalMaxEstSize = stream.Data.Length * 100;
 
             var transform = stream.Data;
+
+            var length = stream.StreamDictionary.GetIntOrDefault(NameToken.Length, -1);
+
+            // If a length is available and it's smaller than the actual data length, use that. This trims whitespace (e.g. newlines) that might have been introduced during transport.
+            // And with that it handles some issues before individual filters have to deal with it.
+            //
+            // Do this before the first filter (to handle cases like multiple filters, etc).
+            if (length > 0 && length < transform.Length)
+            {
+                transform = transform.Slice(0, length);
+            }
+
             for (var i = 0; i < filters.Count; i++)
             {
                 var filter = filters[i];
@@ -89,6 +102,18 @@
             double totalMaxEstSize = stream.Data.Length * 100;
 
             var transform = stream.Data;
+
+            var length = stream.StreamDictionary.GetIntOrDefault(NameToken.Length, -1);
+
+            // If a length is available and it's smaller than the actual data length, use that. This trims whitespace (e.g. newlines) that might have been introduced during transport.
+            // And with that it handles some issues before individual filters have to deal with it.
+            //
+            // Do this before the first filter (to handle cases like multiple filters, etc).
+            if (length > 0 && length < transform.Length)
+            {
+                transform = transform.Slice(0, length);
+            }
+
             for (var i = 0; i < filters.Count; i++)
             {
                 var filter = filters[i];

src/UglyToad.PdfPig/PdfFonts/CidFonts/ICidFont.cs

@@ -57,6 +57,10 @@
 
         TransformationMatrix GetFontMatrix(int characterIdentifier);
 
+        double GetDescent();
+
+        double GetAscent();
+
         /// <summary>
         /// Returns the glyph path for the given character code.
         /// </summary>

src/UglyToad.PdfPig/PdfFonts/CidFonts/ICidFontProgram.cs

@@ -20,6 +20,10 @@
 
         bool TryGetBoundingAdvancedWidth(int characterIdentifier, out double width);
 
+        double? GetDescent();
+
+        double? GetAscent();
+
         bool TryGetPath(int characterCode, [NotNullWhen(true)] out IReadOnlyList<PdfSubpath>? path);
 
         bool TryGetPath(int characterCode, Func<int, int?> characterCodeToGlyphId, [NotNullWhen(true)] out IReadOnlyList<PdfSubpath>? path);

src/UglyToad.PdfPig/PdfFonts/CidFonts/PdfCidCompactFontFormatFont.cs

@@ -42,6 +42,18 @@
 
         public PdfRectangle? GetCharacterBoundingBox(string characterName) => fontCollection.GetCharacterBoundingBox(characterName);
 
+        public double? GetDescent()
+        {
+            // BobLd: we don't support ascent / descent for cff for the moment
+            return null;
+        }
+
+        public double? GetAscent()
+        {
+            // BobLd: we don't support ascent / descent for cff for the moment
+            return null;
+        }
+
         public bool TryGetBoundingBox(int characterIdentifier, out PdfRectangle boundingBox)
         {
             boundingBox = new PdfRectangle(0, 0, 500, 0);

src/UglyToad.PdfPig/PdfFonts/CidFonts/PdfCidTrueTypeFont.cs

@@ -36,6 +36,16 @@
 
         public int GetFontMatrixMultiplier() => font.GetUnitsPerEm();
 
+        public double? GetDescent()
+        {
+            return font.TableRegister.HorizontalHeaderTable.Descent;
+        }
+
+        public double? GetAscent()
+        {
+            return font.TableRegister.HorizontalHeaderTable.Ascent;
+        }
+
         public bool TryGetFontMatrix(int characterCode, [NotNullWhen(true)] out TransformationMatrix? matrix)
         {
             // We don't have a matrix here

src/UglyToad.PdfPig/PdfFonts/CidFonts/Type0CidFont.cs

@@ -148,6 +148,38 @@
             return fontProgram.TryGetFontMatrix(characterIdentifier, out var m) ? m.Value : FontMatrix;
         }
 
+        public double GetDescent()
+        {
+            if (fontProgram is null)
+            {
+                return Descriptor.Descent;
+            }
+
+            double? descent = fontProgram.GetDescent();
+            if (descent.HasValue)
+            {
+                return descent.Value;
+            }
+
+            return Descriptor.Descent;
+        }
+
+        public double GetAscent()
+        {
+            if (fontProgram is null)
+            {
+                return Descriptor.Ascent;
+            }
+
+            double? ascent = fontProgram.GetAscent();
+            if (ascent.HasValue)
+            {
+                return ascent.Value;
+            }
+
+            return Descriptor.Ascent;
+        }
+
         public bool TryGetPath(int characterCode, [NotNullWhen(true)] out IReadOnlyList<PdfSubpath>? path)
         {
             path = null;

src/UglyToad.PdfPig/PdfFonts/CidFonts/Type2CidFont.cs

@@ -132,6 +132,38 @@
             return FontMatrix;
         }
 
+        public double GetDescent()
+        {
+            if (fontProgram is null)
+            {
+                return Descriptor.Descent;
+            }
+
+            double? descent = fontProgram.GetDescent();
+            if (descent.HasValue)
+            {
+                return descent.Value;
+            }
+
+            return Descriptor.Descent;
+        }
+
+        public double GetAscent()
+        {
+            if (fontProgram is null)
+            {
+                return Descriptor.Ascent;
+            }
+
+            double? ascent = fontProgram.GetAscent();
+            if (ascent.HasValue)
+            {
+                return ascent.Value;
+            }
+
+            return Descriptor.Ascent;
+        }
+
         public bool TryGetPath(int characterCode, [NotNullWhen(true)] out IReadOnlyList<PdfSubpath>? path) => TryGetPath(characterCode, cidToGid.GetGlyphIndex, out path);
 
         public bool TryGetPath(int characterCode, Func<int, int?> characterCodeToGlyphId, [NotNullWhen(true)] out IReadOnlyList<PdfSubpath>? path)

src/UglyToad.PdfPig/PdfFonts/Cmap/CharacterMapBuilder.cs

@@ -81,11 +81,15 @@ namespace UglyToad.PdfPig.PdfFonts.Cmap
 
         public CMap Build()
         {
+#if NET
+            BaseFontCharacterMap?.TrimExcess();
+#endif
+
             return new CMap(GetCidSystemInfo(), Type, WMode, Name, Version,
                 BaseFontCharacterMap ?? new Dictionary<int, string>(),
-                CodespaceRanges ?? new CodespaceRange[0],
-                CidRanges ?? new CidRange[0],
-                CidCharacterMappings ?? new CidCharacterMapping[0]);
+                CodespaceRanges ?? Array.Empty<CodespaceRange>(),
+                CidRanges ?? Array.Empty<CidRange>(),
+                CidCharacterMappings ?? Array.Empty<CidCharacterMapping>());
         }
 
         private CharacterIdentifierSystemInfo GetCidSystemInfo()

src/UglyToad.PdfPig/PdfFonts/Composite/Type0Font.cs

@@ -22,6 +22,8 @@
             = new Dictionary<int, CharacterBoundingBox>();
 
         private readonly bool useLenientParsing;
+        private readonly double ascent;
+        private readonly double descent;
 
         public NameToken Name => BaseFont;
 
@@ -57,6 +59,30 @@
                       ?? FontDetails.GetDefault(Name.Data);
 
             useLenientParsing = parsingOptions.UseLenientParsing;
+            ascent = ComputeAscent();
+            descent = ComputeDescent();
+        }
+
+        private double ComputeDescent()
+        {
+            double d = CidFont.GetDescent();
+            if (Math.Abs(d) > double.Epsilon)
+            {
+                return GetFontMatrix().TransformY(d);
+            }
+
+            return -0.25;
+        }
+
+        private double ComputeAscent()
+        {
+            double a = CidFont.GetAscent();
+            if (Math.Abs(a) > double.Epsilon)
+            {
+                return GetFontMatrix().TransformY(a);
+            }
+
+            return 0.75;
         }
 
         public int ReadCharacterCode(IInputBytes bytes, out int codeLength)
@@ -144,6 +170,16 @@
             return CidFont.FontMatrix;
         }
 
+        public double GetDescent()
+        {
+            return descent;
+        }
+
+        public double GetAscent()
+        {
+            return ascent;
+        }
+
         public PdfVector GetPositionVector(int characterCode)
         {
             var characterIdentifier = CMap.ConvertToCid(characterCode);

src/UglyToad.PdfPig/PdfFonts/FontDetails.cs

@@ -3,7 +3,7 @@
     /// <summary>
     /// Summary details of the font used to draw a glyph.
     /// </summary>
-    public class FontDetails
+    public sealed class FontDetails
     {
         /// <summary>
         /// The normal weight for a font.
@@ -35,6 +35,8 @@
         /// </summary>
         public bool IsItalic { get; }
 
+        private readonly Lazy<FontDetails> _bold;
+
         /// <summary>
         /// Create a new <see cref="FontDetails"/>.
         /// </summary>
@@ -44,6 +46,17 @@
             IsBold = isBold;
             Weight = weight;
             IsItalic = isItalic;
+
+            _bold = isBold ? new Lazy<FontDetails>(() => this) : new Lazy<FontDetails>(() => new FontDetails(Name, true, Weight, IsItalic));
+        }
+
+        /// <summary>
+        /// An instance of <see cref="FontDetails"/> with the same properties as the current instance,
+        /// but with the <see cref="IsBold"/> property set to <c>true</c>.
+        /// </summary>
+        public FontDetails AsBold()
+        {
+            return _bold.Value;
         }
 
         internal static FontDetails GetDefault(string? name = null) => new FontDetails(name ?? string.Empty,
@@ -51,7 +64,7 @@
             DefaultWeight,
             false);
 
-        internal FontDetails WithName(string name) => name != null
+        internal FontDetails WithName(string? name) => name is not null
             ? new FontDetails(name, IsBold, Weight, IsItalic)
             : this;
 

src/UglyToad.PdfPig/PdfFonts/IFont.cs

@@ -45,6 +45,24 @@
         /// </summary>
         TransformationMatrix GetFontMatrix();
 
+        /// <summary>
+        /// Retrieves the descent value of the font, adjusted by the font matrix.
+        /// </summary>
+        /// <returns>
+        /// A <see cref="double"/> representing the descent of the font, 
+        /// which is the distance from the baseline to the lowest point of the font's glyphs.
+        /// </returns>
+        double GetDescent();
+
+        /// <summary>
+        /// Retrieves the ascent value of the font, adjusted byt the font matrix.
+        /// </summary>
+        /// <returns>
+        /// A <see cref="double"/> representing the ascent of the font, 
+        /// which is the distance from the baseline to the highest point of the font's glyphs.
+        /// </returns>
+        double GetAscent();
+
         /// <summary>
         /// Returns the glyph path for the given character code.
         /// </summary>

src/UglyToad.PdfPig/PdfFonts/Simple/TrueTypeSimpleFont.cs

@@ -33,6 +33,10 @@
 
         private readonly bool isZapfDingbats;
 
+        private readonly TransformationMatrix fontMatrix;
+        private readonly double descent;
+        private readonly double ascent;
+
 #nullable disable
         public NameToken Name { get; }
 #nullable enable
@@ -66,6 +70,37 @@
                       ?? FontDetails.GetDefault(Name?.Data);
 
             isZapfDingbats = encoding is ZapfDingbatsEncoding || Details.Name.Contains("ZapfDingbats");
+
+            // Set font matrix
+            double scale = 1000.0;
+            if (this.font?.TableRegister.HeaderTable is not null)
+            {
+                scale = this.font.GetUnitsPerEm();
+            }
+
+            fontMatrix = TransformationMatrix.FromValues(1.0 / scale, 0, 0, 1.0 / scale, 0, 0);
+            descent = ComputeDescent();
+            ascent = ComputeAscent();
+        }
+
+        private double ComputeDescent()
+        {
+            if (font is null)
+            {
+                return DefaultTransformation.TransformY(descriptor!.Descent);
+            }
+
+            return GetFontMatrix().TransformY(font.TableRegister.HorizontalHeaderTable.Descent);
+        }
+
+        private double ComputeAscent()
+        {
+            if (font is null)
+            {
+                return DefaultTransformation.TransformY(descriptor!.Ascent);
+            }
+
+            return GetFontMatrix().TransformY(font.TableRegister.HorizontalHeaderTable.Ascent);
         }
 
         public int ReadCharacterCode(IInputBytes bytes, out int codeLength)
@@ -195,14 +230,7 @@
 
         public TransformationMatrix GetFontMatrix()
         {
-            var scale = 1000.0;
-
-            if (font?.TableRegister.HeaderTable != null)
-            {
-                scale = font.GetUnitsPerEm();
-            }
-
-            return TransformationMatrix.FromValues(1 / scale, 0, 0, 1 / scale, 0, 0);
+            return fontMatrix;
         }
 
         private PdfRectangle GetBoundingBoxInGlyphSpace(int characterCode, out bool fromFont)
@@ -338,6 +366,16 @@
             return widths[index];
         }
 
+        public double GetDescent()
+        {
+            return descent;
+        }
+
+        public double GetAscent()
+        {
+            return ascent;
+        }
+
         /// <inheritdoc/>
         public bool TryGetPath(int characterCode, [NotNullWhen(true)] out IReadOnlyList<PdfSubpath>? path)
         {

src/UglyToad.PdfPig/PdfFonts/Simple/TrueTypeStandard14FallbackSimpleFont.cs

@@ -19,6 +19,9 @@
         private static readonly TransformationMatrix DefaultTransformation =
             TransformationMatrix.FromValues(1 / 1000.0, 0, 0, 1 / 1000.0, 0, 0);
 
+        private readonly TransformationMatrix fontMatrix;
+        private readonly double ascent;
+        private readonly double descent;
         private readonly AdobeFontMetrics fontMetrics;
         private readonly Encoding encoding;
         private readonly TrueTypeFont font;
@@ -45,8 +48,42 @@
 
             // Assumption is ZapfDingbats is not possible here. We need to change the behaviour if not the case
             System.Diagnostics.Debug.Assert(!(encoding is ZapfDingbatsEncoding || Details.Name.Contains("ZapfDingbats")));
+
+            // Set font matrix
+            if (this.font?.TableRegister.HeaderTable is not null)
+            {
+                var scale = (double)this.font.GetUnitsPerEm();
+                fontMatrix = TransformationMatrix.FromValues(1.0 / scale, 0, 0, 1.0 / scale, 0, 0);
+            }
+            else
+            {
+                fontMatrix = DefaultTransformation;
+            }
+
+            descent = ComputeDescent();
+            ascent = ComputeAscent();
         }
 
+        private double ComputeDescent()
+        {
+            if (fontMetrics is not null)
+            {
+                return GetFontMatrix().TransformY(fontMetrics.Descender);
+            }
+
+            return GetFontMatrix().TransformY(font.TableRegister.HorizontalHeaderTable.Descent);
+        }
+
+        private double ComputeAscent()
+        {
+            if (fontMetrics is not null)
+            {
+                return GetFontMatrix().TransformY(fontMetrics.Ascender);
+            }
+
+            return GetFontMatrix().TransformY(font.TableRegister.HorizontalHeaderTable.Ascent);
+        }
+        
         public int ReadCharacterCode(IInputBytes bytes, out int codeLength)
         {
             codeLength = 1;
@@ -127,14 +164,17 @@
 
         public TransformationMatrix GetFontMatrix()
         {
-            if (font?.TableRegister.HeaderTable != null)
-            {
-                var scale = (double)font.GetUnitsPerEm();
+            return fontMatrix;
+        }
 
-                return TransformationMatrix.FromValues(1 / scale, 0, 0, 1 / scale, 0, 0);
-            }
+        public double GetDescent()
+        {
+            return descent;
+        }
 
-            return DefaultTransformation;
+        public double GetAscent()
+        {
+            return ascent;
         }
 
         /// <inheritdoc/>

src/UglyToad.PdfPig/PdfFonts/Simple/Type1FontSimple.cs

@@ -36,7 +36,9 @@
         private readonly ToUnicodeCMap toUnicodeCMap;
 
         private readonly TransformationMatrix fontMatrix;
-
+        private readonly double ascent;
+        private readonly double descent;
+        
         private readonly bool isZapfDingbats;
 
         public NameToken Name { get; }
@@ -83,6 +85,60 @@
             Details = fontDescriptor?.ToDetails(name?.Data)
                       ?? FontDetails.GetDefault(name?.Data);
             isZapfDingbats = encoding is ZapfDingbatsEncoding || Details.Name.Contains("ZapfDingbats");
+            descent = ComputeDescent();
+            ascent = ComputeAscent();
+        }
+
+        private double ComputeDescent()
+        {
+            if (Math.Abs(fontDescriptor.Descent) > double.Epsilon)
+            {
+                return fontMatrix.TransformY(fontDescriptor.Descent);
+            }
+
+            /*
+               // BobLd: Should 'fontProgram' be used
+              if (fontProgram is not null)
+              {
+                  if (fontProgram.TryGetFirst(out var t1))
+                  {
+
+                  }
+
+                  if (fontProgram.TryGetSecond(out var cffCol))
+                  {
+
+                  }
+              }
+              */
+
+            return -0.25;
+        }
+
+        private double ComputeAscent()
+        {
+            if (Math.Abs(fontDescriptor.Ascent) > double.Epsilon)
+            {
+                return fontMatrix.TransformY(fontDescriptor.Ascent);
+            }
+
+            /*
+             // BobLd: Should 'fontProgram' be used
+            if (fontProgram is not null)
+            {
+                if (fontProgram.TryGetFirst(out var t1))
+                {
+
+                }
+
+                if (fontProgram.TryGetSecond(out var cffCol))
+                {
+
+                }
+            }
+            */
+
+            return 0.75;
         }
 
         public int ReadCharacterCode(IInputBytes bytes, out int codeLength)
@@ -206,7 +262,7 @@
             {
                 var first = cffFont.FirstFont;
                 string characterName;
-                if (encoding != null)
+                if (encoding is not null)
                 {
                     characterName = encoding.GetName(characterCode);
                 }
@@ -232,6 +288,16 @@
             return fontMatrix;
         }
 
+        public double GetDescent()
+        {
+            return descent;
+        }
+
+        public double GetAscent()
+        {
+            return ascent;
+        }
+
         /// <inheritdoc/>
         public bool TryGetPath(int characterCode, [NotNullWhen(true)] out IReadOnlyList<PdfSubpath>? path)
         {

src/UglyToad.PdfPig/PdfFonts/Simple/Type1Standard14Font.cs

@@ -26,6 +26,8 @@ namespace UglyToad.PdfPig.PdfFonts.Simple
         public FontDetails Details { get; }
 
         private readonly TransformationMatrix fontMatrix = TransformationMatrix.FromValues(0.001, 0, 0, 0.001, 0, 0);
+        private readonly double ascent;
+        private readonly double descent;
 
         public Type1Standard14Font(AdobeFontMetrics standardFontMetrics, Encoding? overrideEncoding = null)
         {
@@ -40,6 +42,28 @@ namespace UglyToad.PdfPig.PdfFonts.Simple
                 standardFontMetrics.Weight == "Bold" ? 700 : FontDetails.DefaultWeight,
                 standardFontMetrics.ItalicAngle != 0);
             isZapfDingbats = encoding is ZapfDingbatsEncoding || Details.Name.Contains("ZapfDingbats");
+            descent = ComputeDescent();
+            ascent = ComputeAscent();
+        }
+
+        private double ComputeDescent()
+        {
+            if (Math.Abs(standardFontMetrics.Descender) < double.Epsilon)
+            {
+                return -0.25;
+            }
+
+            return fontMatrix.TransformY(standardFontMetrics.Descender);
+        }
+
+        private double ComputeAscent()
+        {
+            if (Math.Abs(standardFontMetrics.Ascender) < double.Epsilon)
+            {
+                return 0.75;
+            }
+
+            return fontMatrix.TransformY(standardFontMetrics.Ascender);
         }
 
         public int ReadCharacterCode(IInputBytes bytes, out int codeLength)
@@ -115,6 +139,16 @@ namespace UglyToad.PdfPig.PdfFonts.Simple
             return fontMatrix;
         }
 
+        public double GetDescent()
+        {
+            return descent;
+        }
+
+        public double GetAscent()
+        {
+            return ascent;
+        }
+
         /// <summary>
         /// <inheritdoc/>
         /// <para>Not implemented.</para>

src/UglyToad.PdfPig/PdfFonts/Simple/Type3Font.cs

@@ -13,6 +13,8 @@
     {
         private readonly PdfRectangle boundingBox;
         private readonly TransformationMatrix fontMatrix;
+        private readonly double ascent;
+        private readonly double descent;
         private readonly Encoding encoding;
         private readonly int firstChar;
         private readonly int lastChar;
@@ -45,6 +47,18 @@
 
             // Assumption is ZapfDingbats is not possible here. We need to change the behaviour if not the case
             System.Diagnostics.Debug.Assert(!(encoding is ZapfDingbatsEncoding || Details.Name.Contains("ZapfDingbats")));
+            descent = ComputeDescent();
+            ascent = ComputeAscent();
+        }
+
+        private double ComputeDescent()
+        {
+            return 0;
+        }
+
+        private double ComputeAscent()
+        {
+            return fontMatrix.TransformY(boundingBox.Top);
         }
 
         public int ReadCharacterCode(IInputBytes bytes, out int codeLength)
@@ -106,6 +120,16 @@
             return fontMatrix;
         }
 
+        public double GetDescent()
+        {
+            return descent;
+        }
+
+        public double GetAscent()
+        {
+            return ascent;
+        }
+
         /// <summary>
         /// <inheritdoc/>
         /// <para>Type 3 fonts do not use vector paths. Always returns <c>false</c>.</para>

src/UglyToad.PdfPig/Polyfills/IsExternalInitPoly.cs

@@ -0,0 +1,6 @@
+#if !NET
+namespace System.Runtime.CompilerServices
+{
+    internal static class IsExternalInit { }
+}
+#endif

src/UglyToad.PdfPig/Writer/PdfPageBuilder.cs

@@ -1069,6 +1069,7 @@
                 var letter = new Letter(
                     c.ToString(),
                     documentSpace,
+                    documentSpace,
                     advanceRect.BottomLeft,
                     advanceRect.BottomRight,
                     width,