Implement Modify Clipping operations

src/UglyToad.PdfPig.Core/ClippingRule.cs

@@ -0,0 +1,32 @@
+namespace UglyToad.PdfPig.Core
+{
+    /// <summary>
+    /// Rules for determining which points lie inside/outside a path.
+    /// </summary>
+    public enum ClippingRule
+    {
+        /// <summary>
+        /// No rule.
+        /// </summary>
+        None,
+
+        /// <summary>
+        /// This even-odd rule determines whether a point is inside a path by drawing a ray from that point in 
+        /// any direction and simply counting the number of path segments that cross the ray, regardless of 
+        /// direction. If this number is odd, the point is inside; if even, the point is outside. This yields 
+        /// the same results as the nonzero winding number rule for paths with simple shapes, but produces 
+        /// different results for more complex shapes.
+        /// </summary>
+        EvenOdd,
+
+        /// <summary>
+        /// The nonzero winding number rule determines whether a given point is inside a path by conceptually
+        /// drawing a ray from that point to infinity in any direction and then examining the places where a 
+        /// segment of the path crosses the ray. Starting with a count of 0, the rule adds 1 each time a path 
+        /// segment crosses the ray from left to right and subtracts 1 each time a segment crosses from right 
+        /// to left. After counting all the crossings, if the result is 0, the point is outside the path; 
+        /// otherwise, it is inside.
+        /// </summary>
+        NonZeroWinding
+    }
+}

src/UglyToad.PdfPig.Core/PdfPath.cs

@@ -22,6 +22,16 @@
         /// </summary>
         public bool IsDrawnAsRectangle { get; internal set; }
 
+        /// <summary>
+        /// Rules for determining which points lie inside/outside the path.
+        /// </summary>
+        public ClippingRule ClippingRule { get; private set; }
+
+        /// <summary>
+        /// Returns true if this is a clipping path.
+        /// </summary>
+        public bool IsClipping { get; private set; }
+
         private PdfPoint? currentPosition;
 
         private double shoeLaceSum;
@@ -78,6 +88,16 @@
             return new PdfPoint(points.Average(p => p.X), points.Average(p => p.Y));
         }
 
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="clippingRule"></param>
+        public void SetClipping(ClippingRule clippingRule)
+        {
+            IsClipping = true;
+            ClippingRule = clippingRule;
+        }
+
         internal static PdfPoint GetStartPoint(IPathCommand command)
         {
             if (command is Line line)

src/UglyToad.PdfPig.Tests/Graphics/TestOperationContext.cs

@@ -93,12 +93,14 @@
 
         public void BeginMarkedContent(NameToken name, NameToken propertyDictionaryName, DictionaryToken properties)
         {
-
         }
 
         public void EndMarkedContent()
         {
+        }
 
+        public void ModifyClippingIntersect(ClippingRule clippingRule)
+        {
         }
 
         private class TestFontFactory : IFontFactory

src/UglyToad.PdfPig/Graphics/ContentStreamProcessor.cs

@@ -565,5 +565,10 @@
 
             TextMatrices.TextMatrix = newMatrix;
         }
+
+        public void ModifyClippingIntersect(ClippingRule clippingRule)
+        {
+            CurrentPath.SetClipping(clippingRule);
+        }
     }
 }

src/UglyToad.PdfPig/Graphics/IOperationContext.cs

@@ -127,5 +127,10 @@
         /// Indicates that the current inline image is complete.
         /// </summary>
         void EndInlineImage(IReadOnlyList<byte> bytes);
+
+        /// <summary>
+        /// Modify the clipping rule of the current path.
+        /// </summary>
+        void ModifyClippingIntersect(ClippingRule clippingRule);
     }
 }

src/UglyToad.PdfPig/Graphics/Operations/ClippingPaths/ModifyClippingByEvenOddIntersect.cs

@@ -29,6 +29,7 @@
         /// <inheritdoc />
         public void Run(IOperationContext operationContext)
         {
+            operationContext.ModifyClippingIntersect(PdfPig.Core.ClippingRule.EvenOdd);
         }
 
         /// <inheritdoc />

src/UglyToad.PdfPig/Graphics/Operations/ClippingPaths/ModifyClippingByNonZeroWindingIntersect.cs

@@ -29,6 +29,7 @@
         /// <inheritdoc />
         public void Run(IOperationContext operationContext)
         {
+            operationContext.ModifyClippingIntersect(PdfPig.Core.ClippingRule.NonZeroWinding);
         }
 
         /// <inheritdoc />