From ae55dbed466dda8ba20592073df0cdc8de97aea2 Mon Sep 17 00:00:00 2001
From: Drawaes <seawardtim@gmail.com>
Date: Fri, 28 Apr 2017 03:33:20 +0100
Subject: [PATCH] Fixed interlaced PNG

---
 src/ImageSharp/Formats/Png/PngDecoderCore.cs       | 14 ++++++++++++--
 src/ImageSharp/Formats/Png/Zlib/Adler32.cs         |  2 +-
 .../{DeframeStream.cs => ZlibInflateStream.cs}     |  6 +++---
 3 files changed, 16 insertions(+), 6 deletions(-)
 rename src/ImageSharp/Formats/Png/Zlib/{DeframeStream.cs => ZlibInflateStream.cs} (97%)

diff --git a/src/ImageSharp/Formats/Png/PngDecoderCore.cs b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
index aece86700..05ba5ee60 100644
--- a/src/ImageSharp/Formats/Png/PngDecoderCore.cs
+++ b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
@@ -191,7 +191,7 @@ namespace ImageSharp.Formats
             PixelAccessor<TPixel> pixels = null;
             try
             {
-                using (DeframeStream deframeStream = new DeframeStream(this.currentStream))
+                using (ZlibInflateStream deframeStream = new ZlibInflateStream(this.currentStream))
                 {
                     PngChunk currentChunk;
                     while (!this.isEndChunkReached && (currentChunk = this.ReadChunk()) != null)
@@ -492,12 +492,14 @@ namespace ImageSharp.Formats
         private void DecodeInterlacedPixelData<TPixel>(Stream compressedStream, PixelAccessor<TPixel> pixels)
             where TPixel : struct, IPixel<TPixel>
         {
-            while (this.pass < 7)
+            while (true)
             {
                 int numColumns = this.ComputeColumnsAdam7(this.pass);
 
                 if (numColumns == 0)
                 {
+                    this.pass++;
+
                     // This pass contains no data; skip to next pass
                     continue;
                 }
@@ -561,6 +563,14 @@ namespace ImageSharp.Formats
                 }
 
                 this.pass++;
+                if (this.pass < 7)
+                {
+                    this.currentRow = Adam7FirstRow[this.pass];
+                }
+                else
+                {
+                    break;
+                }
             }
         }
 
diff --git a/src/ImageSharp/Formats/Png/Zlib/Adler32.cs b/src/ImageSharp/Formats/Png/Zlib/Adler32.cs
index 56b116cd3..5f92cc9e0 100644
--- a/src/ImageSharp/Formats/Png/Zlib/Adler32.cs
+++ b/src/ImageSharp/Formats/Png/Zlib/Adler32.cs
@@ -52,7 +52,7 @@ namespace ImageSharp.Formats
     ///    checked separately. (Any sequence of zeroes has a Fletcher
     ///    checksum of zero.)"
     /// </remarks>
-    /// <see cref="DeframeStream"/>
+    /// <see cref="ZlibInflateStream"/>
     /// <see cref="ZlibDeflateStream"/>
     internal sealed class Adler32 : IChecksum
     {
diff --git a/src/ImageSharp/Formats/Png/Zlib/DeframeStream.cs b/src/ImageSharp/Formats/Png/Zlib/ZlibInflateStream.cs
similarity index 97%
rename from src/ImageSharp/Formats/Png/Zlib/DeframeStream.cs
rename to src/ImageSharp/Formats/Png/Zlib/ZlibInflateStream.cs
index 2e92fd52d..0743d8ded 100644
--- a/src/ImageSharp/Formats/Png/Zlib/DeframeStream.cs
+++ b/src/ImageSharp/Formats/Png/Zlib/ZlibInflateStream.cs
@@ -9,7 +9,7 @@
     /// <summary>
     /// Provides methods and properties for deframing streams from PNGs.
     /// </summary>
-    internal class DeframeStream : Stream
+    internal class ZlibInflateStream : Stream
     {
         /// <summary>
         /// The inner raw memory stream
@@ -45,10 +45,10 @@
         private int currentDataRemaining;
 
         /// <summary>
-        /// Initializes a new instance of the <see cref="DeframeStream"/> class.
+        /// Initializes a new instance of the <see cref="ZlibInflateStream"/> class.
         /// </summary>
         /// <param name="innerStream">The inner raw stream</param>
-        public DeframeStream(Stream innerStream)
+        public ZlibInflateStream(Stream innerStream)
         {
             this.innerStream = innerStream;
         }