#48 add handling of inline image data to pdf content parsing

an inline image in a pdf content stream starts with the bi tag, then id declares the start of image data and ei the end. attempting to parse the bytes after the id tag as usual resulted in errors. this change adds special case handling for inline images.

src/UglyToad.PdfPig/Geometry/PdfPath.cs

@@ -5,19 +5,28 @@ namespace UglyToad.PdfPig.Geometry
     using System.Collections.Generic;
     using System.Linq;
     using System.Text;
-    using UglyToad.PdfPig.Core;
+    using Core;
 
     /// <summary>
-    /// A path in a PDF document, used by glyphs and page content.
+    /// A path in a PDF document, used by glyphs and page content. Can contain multiple sub-paths.
     /// </summary>
     public class PdfPath
     {
         private readonly List<IPathCommand> commands = new List<IPathCommand>();
+
+        /// <summary>
+        /// The sequence of sub-paths which form this <see cref="PdfPath"/>.
+        /// </summary>
         public IReadOnlyList<IPathCommand> Commands => commands;
 
         private PdfPoint? currentPosition;
-        private TransformationMatrix currentTransformationMatrix = TransformationMatrix.Identity;
 
+        private readonly TransformationMatrix currentTransformationMatrix;
+
+        /// <summary>
+        /// Create a new <see cref="PdfPath"/>.
+        /// </summary>
+        /// <param name="transformationMatrix">The transformation to apply to all points in this path.</param>
         public PdfPath(TransformationMatrix transformationMatrix)
         {
             currentTransformationMatrix = transformationMatrix;
@@ -162,79 +171,140 @@ namespace UglyToad.PdfPig.Geometry
             return result;
         }
 
+        /// <summary>
+        /// A command in a <see cref="PdfPath"/>.
+        /// </summary>
         public interface IPathCommand
         {
+            /// <summary>
+            /// Returns the smallest rectangle which contains the path region given by this command.
+            /// </summary>
+            /// <returns></returns>
             PdfRectangle? GetBoundingRectangle();
 
+            /// <summary>
+            /// Converts from the path command to an SVG string representing the path operation.
+            /// </summary>
             void WriteSvg(StringBuilder builder);
         }
 
-        private class Close : IPathCommand
+        /// <summary>
+        /// Close the current <see cref="PdfPath"/>.
+        /// </summary>
+        public class Close : IPathCommand
         {
+            /// <inheritdoc />
             public PdfRectangle? GetBoundingRectangle()
             {
                 return null;
             }
 
+            /// <inheritdoc />
             public void WriteSvg(StringBuilder builder)
             {
                 builder.Append("Z ");
             }
         }
 
+        /// <summary>
+        /// Move drawing of the current <see cref="PdfPath"/> to the specified location.
+        /// </summary>
         public class Move : IPathCommand
         {
+            /// <summary>
+            /// The location to move to.
+            /// </summary>
             public PdfPoint Location { get; }
 
+            /// <summary>
+            /// Create a new <see cref="Move"/> path command.
+            /// </summary>
+            /// <param name="location"></param>
             public Move(PdfPoint location)
             {
                 Location = location;
             }
 
+            /// <summary>
+            /// Returns <see langword="null"/> since this generates no visible path.
+            /// </summary>
             public PdfRectangle? GetBoundingRectangle()
             {
                 return null;
             }
 
+            /// <inheritdoc />
             public void WriteSvg(StringBuilder builder)
             {
                 builder.Append("M ").Append(Location.X).Append(' ').Append(Location.Y).Append(' ');
             }
         }
 
+        /// <summary>
+        /// Draw a straight line between two points.
+        /// </summary>
         public class Line : IPathCommand
         {
+            /// <summary>
+            /// The start of the line.
+            /// </summary>
             public PdfPoint From { get; }
 
+            /// <summary>
+            /// The end of the line.
+            /// </summary>
             public PdfPoint To { get; }
 
+            /// <summary>
+            /// Create a new <see cref="Line"/>.
+            /// </summary>
             public Line(PdfPoint from, PdfPoint to)
             {
                 From = from;
                 To = to;
             }
 
+            /// <inheritdoc />
             public PdfRectangle? GetBoundingRectangle()
             {
                 return new PdfRectangle(From, To);
             }
 
+            /// <inheritdoc />
             public void WriteSvg(StringBuilder builder)
             {
                 builder.AppendFormat("L {0} {1} ", To.X, To.Y);
             }
         }
 
+        /// <summary>
+        /// Draw a Bezier curve given by the start, control and end points.
+        /// </summary>
         public class BezierCurve : IPathCommand
         {
+            /// <summary>
+            /// The start point of the Bezier curve.
+            /// </summary>
             public PdfPoint StartPoint { get; }
 
+            /// <summary>
+            /// The first control point of the curve.
+            /// </summary>
             public PdfPoint FirstControlPoint { get; }
 
+            /// <summary>
+            /// The second control point of the curve.
+            /// </summary>
             public PdfPoint SecondControlPoint { get; }
 
+            /// <summary>
+            /// The end point of the curve.
+            /// </summary>
             public PdfPoint EndPoint { get; }
 
+            /// <summary>
+            /// Create a Bezier curve at the provided points.
+            /// </summary>
             public BezierCurve(PdfPoint startPoint, PdfPoint firstControlPoint, PdfPoint secondControlPoint, PdfPoint endPoint)
             {
                 StartPoint = startPoint;
@@ -243,6 +313,7 @@ namespace UglyToad.PdfPig.Geometry
                 EndPoint = endPoint;
             }
 
+            /// <inheritdoc />
             public PdfRectangle? GetBoundingRectangle()
             {
                 // Optimised
@@ -287,6 +358,13 @@ namespace UglyToad.PdfPig.Geometry
                 return new PdfRectangle((decimal)minX, (decimal)minY, (decimal)maxX, (decimal)maxY);
             }
 
+            /// <inheritdoc />
+            public void WriteSvg(StringBuilder builder)
+            {
+                builder.AppendFormat("C {0} {1}, {2} {3}, {4} {5} ", FirstControlPoint.X, FirstControlPoint.Y, SecondControlPoint.X, SecondControlPoint.Y,
+                    EndPoint.X, EndPoint.Y);
+            }
+
 
             private bool TrySolveQuadratic(bool isX, double currentMin, double currentMax, out (double min, double max) solutions)
             {
@@ -378,12 +456,6 @@ namespace UglyToad.PdfPig.Geometry
 
                 return p;
             }
-
-            public void WriteSvg(StringBuilder builder)
-            {
-                builder.AppendFormat("C {0} {1}, {2} {3}, {4} {5} ", FirstControlPoint.X, FirstControlPoint.Y, SecondControlPoint.X, SecondControlPoint.Y,
-                    EndPoint.X, EndPoint.Y);
-            }
         }
 
         internal void Rectangle(decimal x, decimal y, decimal width, decimal height)