more end image recovery logic

since inline image data may contain the end image "ei" token inside the data stream there's no reliable way to actually determine if we've read all the data. for this reason if we end up with an invalid state parsing operations after we've read the end image token we try to recover by reading from the previous token to the next end image token if any. we supply log information to let the consumer know this is what we're doing. it's still not bullet-proof but it should be good enough.

also support negative page rotation values by adding them to a 360 degree rotation so -90 degrees clockwise is 270 degrees clockwise.

src/UglyToad.PdfPig.Tokenization/Scanner/CoreTokenScanner.cs

@@ -220,6 +220,46 @@
             customTokenizers.RemoveAll(x => ReferenceEquals(x.tokenizer, tokenizer));
         }
 
+        /// <summary>
+        /// Handles the situation where "EI" was encountered in the inline image data but was
+        /// not the end of the image.
+        /// </summary>
+        /// <param name="lastEndImageOffset">The offset of the "E" of the "EI" marker which was incorrectly read.</param>
+        /// <returns>The set of bytes from the incorrect "EI" to the correct "EI" including the incorrect "EI".</returns>
+        public IReadOnlyList<byte> RecoverFromIncorrectEndImage(long lastEndImageOffset)
+        {
+            var data = new List<byte>();
+
+            inputBytes.Seek(lastEndImageOffset);
+            
+            if (!inputBytes.MoveNext() || inputBytes.CurrentByte != 'E')
+            {
+                var message = $"Failed to recover the image data stream for an inline image at offset {lastEndImageOffset}. " +
+                              $"Expected to read byte 'E' instead got {inputBytes.CurrentByte}.";
+
+                throw new PdfDocumentFormatException(message);
+            }
+
+            data.Add(inputBytes.CurrentByte);
+
+            if (!inputBytes.MoveNext() || inputBytes.CurrentByte != 'I')
+            {
+                var message = $"Failed to recover the image data stream for an inline image at offset {lastEndImageOffset}. " +
+                              $"Expected to read second byte 'I' following 'E' instead got {inputBytes.CurrentByte}.";
+
+                throw new PdfDocumentFormatException(message);
+            }
+
+            data.Add(inputBytes.CurrentByte);
+
+            data.AddRange(ReadUntilEndImage(lastEndImageOffset));
+
+            // Skip beyond the 'I' in the "EI" token we just read so the scanner is in a valid position.
+            inputBytes.MoveNext();
+
+            return data;
+        }
+
         private IReadOnlyList<byte> ReadInlineImageData()
         {
             // The ID operator should be followed by a single white-space character, and the next character is interpreted
@@ -231,9 +271,14 @@
 
             var startsAt = inputBytes.CurrentOffset - 2;
 
+            return ReadUntilEndImage(startsAt);
+        }
+
+        private List<byte> ReadUntilEndImage(long startsAt)
+        {
             const byte lastPlainText = 127;
             const byte space = 32;
-            
+
 
             var imageData = new List<byte>();
             byte prevByte = 0;