Make geometric transforms consistent with PDF specification

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

@@ -270,10 +270,10 @@ public void SetWordSpacing(double spacing)
             GetCurrentState().FontState.WordSpacing = spacing;
         }
 
-        public void ModifyCurrentTransformationMatrix(double[] value)
+        public void ModifyCurrentTransformationMatrix(TransformationMatrix value)
         {
-            var ctm = GetCurrentState().CurrentTransformationMatrix;
-            GetCurrentState().CurrentTransformationMatrix = TransformationMatrix.FromArray(value).Multiply(ctm);
+            var state = GetCurrentState();
+            state.CurrentTransformationMatrix = value.Multiply(state.CurrentTransformationMatrix);
         }
 
         public void SetCharacterSpacing(double spacing)

src/UglyToad.PdfPig/Graphics/BaseStreamProcessor.cs

@@ -563,8 +563,8 @@ protected virtual void ProcessFormXObject(StreamToken formStream, NameToken xObj
                         .ToArray());
             }
 
-            // 2. Update current transformation matrix.
-            startState.CurrentTransformationMatrix = formMatrix.Multiply(startState.CurrentTransformationMatrix);
+            // 2. Update current transformation matrix.
+            ModifyCurrentTransformationMatrix(formMatrix);
 
             var contentStream = formStream.Decode(FilterProvider, PdfScanner);
 
@@ -576,9 +576,8 @@ protected virtual void ProcessFormXObject(StreamToken formStream, NameToken xObj
             if (formStream.StreamDictionary.TryGet<ArrayToken>(NameToken.Bbox, PdfScanner, out var bboxToken))
             {
                 var points = bboxToken.Data.OfType<NumericToken>().Select(x => x.Double).ToArray();
-                PdfRectangle bbox = new PdfRectangle(points[0], points[1], points[2], points[3]);
-                PdfRectangle transformedBox = startState.CurrentTransformationMatrix.Transform(bbox).Normalise();
-                ClipToRectangle(transformedBox, FillingRule.EvenOdd); // TODO - Check that Even Odd is valid
+                PdfRectangle bbox = new PdfRectangle(points[0], points[1], points[2], points[3]).Normalise();
+                ClipToRectangle(bbox, FillingRule.EvenOdd); // TODO - Check that Even Odd is valid
             }
 
             // 4. Paint the objects.
@@ -958,10 +957,10 @@ public virtual void SetWordSpacing(double spacing)
         }
 
         /// <inheritdoc/>
-        public virtual void ModifyCurrentTransformationMatrix(double[] value)
+        public virtual void ModifyCurrentTransformationMatrix(TransformationMatrix value)
         {
-            var ctm = GetCurrentState().CurrentTransformationMatrix;
-            GetCurrentState().CurrentTransformationMatrix = TransformationMatrix.FromArray(value).Multiply(ctm);
+            var state = GetCurrentState();
+            state.CurrentTransformationMatrix = value.Multiply(state.CurrentTransformationMatrix);
         }
 
         /// <inheritdoc/>

src/UglyToad.PdfPig/Graphics/ContentStreamProcessor.cs

@@ -452,6 +452,7 @@ protected override void ClipToRectangle(PdfRectangle rectangle, FillingRule clip
         {
             // https://github.com/apache/pdfbox/blob/f4bfe47de37f6fe69e8f98b164c3546facfd5e91/pdfbox/src/main/java/org/apache/pdfbox/contentstream/PDFStreamEngine.java#L611
             var graphicsState = GetCurrentState();
+            rectangle = graphicsState.CurrentTransformationMatrix.Transform(rectangle).Normalise();
             var clip = rectangle.ToPdfPath();
             clip.SetClipping(clippingRule);
 

src/UglyToad.PdfPig/Graphics/IOperationContext.cs

@@ -243,7 +243,7 @@ public interface IOperationContext
         /// <summary>
         /// Modify the current transformation matrix by concatenating the specified matrix.
         /// </summary>
-        void ModifyCurrentTransformationMatrix(double[] value);
+        void ModifyCurrentTransformationMatrix(TransformationMatrix value);
 
         /// <summary>
         /// Set the character spacing to a number expressed in unscaled text space units.

src/UglyToad.PdfPig/Graphics/Operations/SpecialGraphicsState/ModifyCurrentTransformationMatrix.cs

@@ -2,6 +2,7 @@
 {
     using System;
     using System.IO;
+    using PdfPig.Core;
 
     /// <inheritdoc />
     /// <summary>
@@ -43,7 +44,7 @@ public ModifyCurrentTransformationMatrix(double[] value)
         /// <inheritdoc />
         public void Run(IOperationContext operationContext)
         {
-            operationContext.ModifyCurrentTransformationMatrix(Value);
+            operationContext.ModifyCurrentTransformationMatrix(TransformationMatrix.FromArray(Value));
         }
 
         /// <inheritdoc />