Merge pull request #220 from BobLd/fix-clip-line-fill

fix clipping error when trying to fill a single line

src/UglyToad.PdfPig.Tests/Geometry/ClippingTests.cs

@@ -0,0 +1,19 @@
+using UglyToad.PdfPig.Tests.Integration;
+using Xunit;
+
+namespace UglyToad.PdfPig.Tests.Geometry
+{
+    public class ClippingTests
+    {
+        [Fact]
+        public void ContainsRectangleEvenOdd()
+        {
+            using (var document = PdfDocument.Open(IntegrationHelpers.GetDocumentPath("SPARC - v9 Architecture Manual"),
+                new ParsingOptions() { ClipPaths = true }))
+            {
+                var page = document.GetPage(45);
+                Assert.Equal(28, page.ExperimentalAccess.Paths.Count);
+            }
+        }
+    }
+}

src/UglyToad.PdfPig/Geometry/ClippingExtensions.cs

@@ -6,6 +6,7 @@
     using ClipperLibrary;
     using Core;
     using Graphics;
+    using UglyToad.PdfPig.Logging;
     using static Core.PdfSubpath;
 
     /// <summary>
@@ -23,7 +24,7 @@
         /// <summary>
         /// Generates the result of applying a clipping path to another path.
         /// </summary>
-        public static PdfPath Clip(this PdfPath clipping, PdfPath subject)
+        public static PdfPath Clip(this PdfPath clipping, PdfPath subject, ILog log = null)
         {
             if (clipping == null)
             {
@@ -61,7 +62,10 @@
                     subPathClipping.CloseSubpath();
                 }
 
-                clipper.AddPath(subPathClipping.ToClipperPolygon().ToList(), ClipperPolyType.Clip, true);
+                if (!clipper.AddPath(subPathClipping.ToClipperPolygon().ToList(), ClipperPolyType.Clip, true))
+                {
+                    log?.Error("ClippingExtensions.Clip(): failed to add clipping subpath.");
+                }
             }
 
             // Subject path
@@ -74,13 +78,27 @@
                     continue;
                 }
 
+                if (subjectClose && !subPathSubject.IsClosed()
+                    && subPathSubject.Commands.Count(sp => sp is Line) < 2
+                    && subPathSubject.Commands.Count(sp => sp is BezierCurve) == 0)
+                {
+                    // strange here:
+                    // the subpath contains maximum 1 line and no curves
+                    // it cannot be filled or a be clipping path
+                    // cancel closing the path/subpath
+                    subjectClose = false;
+                }
+
                 // Force close subject if need be
                 if (subjectClose && !subPathSubject.IsClosed())
                 {
                     subPathSubject.CloseSubpath();
                 }
 
-                clipper.AddPath(subPathSubject.ToClipperPolygon().ToList(), ClipperPolyType.Subject, subjectClose);
+                if (!clipper.AddPath(subPathSubject.ToClipperPolygon().ToList(), ClipperPolyType.Subject, subjectClose))
+                {
+                    log?.Error("ClippingExtensions.Clip(): failed to add subject subpath for clipping.");
+                }
             }
 
             var clippingFillType = clipping.FillingRule == FillingRule.NonZeroWinding ? ClipperPolyFillType.NonZero : ClipperPolyFillType.EvenOdd;
@@ -164,11 +182,12 @@
                 yield break;
             }
 
-            if (pdfPath.Commands[0] is Move currentMove)
+            ClipperIntPoint movePoint;
+            if (pdfPath.Commands[0] is Move move)
             {
-                var previous = currentMove.Location.ToClipperIntPoint();
+                movePoint = move.Location.ToClipperIntPoint();
 
-                yield return previous;
+                yield return movePoint;
 
                 if (pdfPath.Commands.Count == 1)
                 {
@@ -185,7 +204,7 @@
                 var command = pdfPath.Commands[i];
                 if (command is Move)
                 {
-                    throw new ArgumentException("ToClipperPolygon():only one move allowed per subpath.", nameof(pdfPath));
+                    throw new ArgumentException("ToClipperPolygon(): only one move allowed per subpath.", nameof(pdfPath));
                 }
 
                 if (command is Line line)
@@ -203,7 +222,11 @@
                 }
                 else if (command is Close)
                 {
-                    yield return currentMove.Location.ToClipperIntPoint();
+                    if (movePoint == null)
+                    {
+                        throw new ArgumentException("ToClipperPolygon(): Move command was null, cannot close the subpath.");
+                    }
+                    yield return movePoint;
                 }
             }
         }

src/UglyToad.PdfPig/Graphics/ContentStreamProcessor.cs

@@ -106,7 +106,7 @@
             var clippingSubpath = new PdfSubpath();
             clippingSubpath.Rectangle(cropBox.BottomLeft.X, cropBox.BottomLeft.Y, cropBox.Width, cropBox.Height);
             var clippingPath = new PdfPath() { clippingSubpath };
-            clippingPath.SetClipping(FillingRule.NonZeroWinding);
+            clippingPath.SetClipping(FillingRule.EvenOdd);
 
             graphicsStack.Push(new CurrentGraphicsState()
             {
@@ -627,7 +627,7 @@
 
             if (clipPaths)
             {
-                var clippedPath = currentState.CurrentClippingPath.Clip(CurrentPath);
+                var clippedPath = currentState.CurrentClippingPath.Clip(CurrentPath, log);
                 if (clippedPath != null)
                 {
                     paths.Add(clippedPath);
@@ -658,7 +658,7 @@
                 var currentClipping = GetCurrentState().CurrentClippingPath;
                 currentClipping.SetClipping(clippingRule);
 
-                var newClippings = CurrentPath.Clip(currentClipping);
+                var newClippings = CurrentPath.Clip(currentClipping, log);
                 if (newClippings == null)
                 {
                     log.Warn("Empty clipping path found. Clipping path not updated.");