Add GetDescent() and GetAscent() methods to IFont, improve font matrix for TrueTypeSimpleFont and TrueTypeStandard14FallbackSimpleFont and add loose bounding box to Letter

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/TextExtractor/ContentOrderTextExtractor.cs

@@ -60,6 +60,7 @@
                     letter = new Letter(
                         " ",
                         letter.GlyphRectangle,
+                        letter.GlyphRectangleLoose,
                         letter.StartBaseLine,
                         letter.EndBaseLine,
                         letter.Width,

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

@@ -60,6 +60,7 @@
         private static TextBlock CreateFakeTextBlock(PdfRectangle boundingBox)
         {
             var letter = new Letter("a",
+                boundingBox,
                 boundingBox,
                 boundingBox.BottomLeft,
                 boundingBox.BottomRight,

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
     {
@@ -69,6 +70,9 @@ namespace UglyToad.PdfPig.Tests.Fonts.SystemFonts
                     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.True(current.GlyphRectangle.IntersectsWith(current.GlyphRectangleLoose));
+                    Assert.Equal(current.GlyphRectangle.Rotation, current.GlyphRectangleLoose.Rotation, 3);
                 }
             }
         }

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

@@ -193,6 +193,32 @@
                         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);
+                    }
+                }
             }
         }
 

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/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>
@@ -110,6 +116,7 @@
         /// </summary>
         public Letter(string value,
             PdfRectangle glyphRectangle,
+            PdfRectangle glyphRectangleLoose,
             PdfPoint startBaseLine,
             PdfPoint endBaseLine,
             double width,
@@ -120,7 +127,7 @@
             IColor fillColor,
             double pointSize,
             int textSequence) :
-                this(value, glyphRectangle,
+                this(value, glyphRectangle, glyphRectangleLoose,
                     startBaseLine, endBaseLine,
                     width, fontSize, font.Details, font,
                     renderingMode, strokeColor, fillColor,
@@ -132,6 +139,7 @@
         /// </summary>
         public Letter(string value,
             PdfRectangle glyphRectangle,
+            PdfRectangle glyphRectangleLoose,
             PdfPoint startBaseLine,
             PdfPoint endBaseLine,
             double width,
@@ -142,14 +150,16 @@
             IColor fillColor,
             double pointSize,
             int textSequence): 
-                this(value, glyphRectangle,
+                this(value, glyphRectangle, glyphRectangleLoose,
                     startBaseLine, endBaseLine,
                     width, fontSize, fontDetails, null,
                     renderingMode, strokeColor, fillColor,
                     pointSize, textSequence)
         { }
 
-        private Letter(string value, PdfRectangle glyphRectangle,
+        private Letter(string value,
+            PdfRectangle glyphRectangle,
+            PdfRectangle glyphRectangleLoose,
             PdfPoint startBaseLine,
             PdfPoint endBaseLine,
             double width,
@@ -164,6 +174,7 @@
         {
             Value = value;
             GlyphRectangle = glyphRectangle;
+            GlyphRectangleLoose = glyphRectangleLoose;
             StartBaseLine = startBaseLine;
             EndBaseLine = endBaseLine;
             Width = width;
@@ -197,6 +208,7 @@
         {
             return new Letter(Value,
                 GlyphRectangle,
+                GlyphRectangleLoose,
                 StartBaseLine,
                 EndBaseLine,
                 Width,

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;
@@ -129,6 +123,7 @@ namespace UglyToad.PdfPig.Graphics
                     letter = new Letter(
                         newLetter,
                         attachTo.GlyphRectangle,
+                        attachTo.GlyphRectangleLoose,
                         attachTo.StartBaseLine,
                         attachTo.EndBaseLine,
                         attachTo.Width,
@@ -151,9 +146,25 @@ 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,
@@ -167,7 +178,6 @@ namespace UglyToad.PdfPig.Graphics
             }
 
             letters.Add(letter);
-
             markedContentStack.AddLetter(letter);
         }
 

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/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/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;
@@ -45,6 +48,40 @@
 
             // 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)
@@ -127,14 +164,17 @@
 
         public TransformationMatrix GetFontMatrix()
         {
-            if (font?.TableRegister.HeaderTable != null)
-            {
-                var scale = (double)font.GetUnitsPerEm();
-
-                return TransformationMatrix.FromValues(1 / scale, 0, 0, 1 / scale, 0, 0);
+            return fontMatrix;
         }
 
-            return DefaultTransformation;
+        public double GetDescent()
+        {
+            return descent;
+        }
+
+        public double GetAscent()
+        {
+            return ascent;
         }
 
         /// <inheritdoc/>

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

@@ -36,6 +36,8 @@
         private readonly ToUnicodeCMap toUnicodeCMap;
 
         private readonly TransformationMatrix fontMatrix;
+        private readonly double ascent;
+        private readonly double descent;
         
         private readonly bool isZapfDingbats;
 
@@ -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.Height);
         }
 
         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/Writer/PdfPageBuilder.cs

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