diff --git a/src/ImageSharp/Formats/Png/PngDecoderCore.cs b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
index a9e588f6e..037f648f0 100644
--- a/src/ImageSharp/Formats/Png/PngDecoderCore.cs
+++ b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
@@ -5,6 +5,7 @@ using System;
using System.Buffers.Binary;
using System.Collections.Generic;
using System.IO;
+using System.IO.Compression;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Text;
@@ -175,18 +176,7 @@ namespace SixLabors.ImageSharp.Formats.Png
this.InitializeImage(metadata, out image);
}
- var deframeStream = new ZlibInflateStream(this.currentStream, this.ReadNextDataChunk);
- try
- {
- deframeStream.AllocateNewBytes(chunk.Length, true);
- this.ReadScanlines(deframeStream.CompressedStream, image.Frames.RootFrame, pngMetadata);
- }
- finally
- {
- // If an invalid Zlib stream is discovered the decoder will throw an exception
- // due to the critical nature of the data chunk.
- deframeStream.Dispose();
- }
+ this.ReadScanlines(chunk, image.Frames.RootFrame, pngMetadata);
break;
case PngChunkType.Palette:
@@ -472,19 +462,25 @@ namespace SixLabors.ImageSharp.Formats.Png
/// Reads the scanlines within the image.
///
/// The pixel format.
- /// The containing data.
+ /// The png chunk containing the compressed scanline data.
/// The pixel data.
/// The png metadata
- private void ReadScanlines(Stream dataStream, ImageFrame image, PngMetadata pngMetadata)
+ private void ReadScanlines(PngChunk chunk, ImageFrame image, PngMetadata pngMetadata)
where TPixel : struct, IPixel
{
- if (this.header.InterlaceMethod == PngInterlaceMode.Adam7)
- {
- this.DecodeInterlacedPixelData(dataStream, image, pngMetadata);
- }
- else
+ using (var deframeStream = new ZlibInflateStream(this.currentStream, this.ReadNextDataChunk))
{
- this.DecodePixelData(dataStream, image, pngMetadata);
+ deframeStream.AllocateNewBytes(chunk.Length, true);
+ DeflateStream dataStream = deframeStream.CompressedStream;
+
+ if (this.header.InterlaceMethod == PngInterlaceMode.Adam7)
+ {
+ this.DecodeInterlacedPixelData(dataStream, image, pngMetadata);
+ }
+ else
+ {
+ this.DecodePixelData(dataStream, image, pngMetadata);
+ }
}
}
@@ -1021,7 +1017,7 @@ namespace SixLabors.ImageSharp.Formats.Png
private bool TryUncompressTextData(ReadOnlySpan compressedData, Encoding encoding, out string value)
{
using (var memoryStream = new MemoryStream(compressedData.ToArray()))
- using (var inflateStream = new ZlibInflateStream(memoryStream, () => 0))
+ using (var inflateStream = new ZlibInflateStream(memoryStream))
{
if (!inflateStream.AllocateNewBytes(compressedData.Length, false))
{
diff --git a/src/ImageSharp/Formats/Png/Zlib/ZlibInflateStream.cs b/src/ImageSharp/Formats/Png/Zlib/ZlibInflateStream.cs
index df0e72332..e4645c44a 100644
--- a/src/ImageSharp/Formats/Png/Zlib/ZlibInflateStream.cs
+++ b/src/ImageSharp/Formats/Png/Zlib/ZlibInflateStream.cs
@@ -20,14 +20,14 @@ namespace SixLabors.ImageSharp.Formats.Png.Zlib
private static readonly byte[] ChecksumBuffer = new byte[4];
///
- /// The inner raw memory stream
+ /// A default delegate to get more data from the inner stream.
///
- private readonly Stream innerStream;
+ private static readonly Func GetDataNoOp = () => 0;
///
- /// The compressed stream sitting over the top of the deframer
+ /// The inner raw memory stream
///
- private DeflateStream compressedStream;
+ private readonly Stream innerStream;
///
/// A value indicating whether this instance of the given entity has been disposed.
@@ -55,8 +55,17 @@ namespace SixLabors.ImageSharp.Formats.Png.Zlib
///
/// Initializes a new instance of the class.
///
- /// The inner raw stream
- /// A delegate to get more data from the inner stream
+ /// The inner raw stream.
+ public ZlibInflateStream(Stream innerStream)
+ : this(innerStream, GetDataNoOp)
+ {
+ }
+
+ ///
+ /// Initializes a new instance of the class.
+ ///
+ /// The inner raw stream.
+ /// A delegate to get more data from the inner stream.
public ZlibInflateStream(Stream innerStream, Func getData)
{
this.innerStream = innerStream;
@@ -76,12 +85,12 @@ namespace SixLabors.ImageSharp.Formats.Png.Zlib
public override long Length => throw new NotSupportedException();
///
- public override long Position { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
+ public override long Position { get => throw new NotSupportedException(); set => throw new NotSupportedException(); }
///
/// Gets the compressed stream over the deframed inner stream
///
- public DeflateStream CompressedStream => this.compressedStream;
+ public DeflateStream CompressedStream { get; private set; }
///
/// Adds new bytes from a frame found in the original stream
@@ -92,7 +101,7 @@ namespace SixLabors.ImageSharp.Formats.Png.Zlib
public bool AllocateNewBytes(int bytes, bool isCriticalChunk)
{
this.currentDataRemaining = bytes;
- if (this.compressedStream is null)
+ if (this.CompressedStream is null)
{
return this.InitializeInflateStream(isCriticalChunk);
}
@@ -101,10 +110,7 @@ namespace SixLabors.ImageSharp.Formats.Png.Zlib
}
///
- public override void Flush()
- {
- throw new NotSupportedException();
- }
+ public override void Flush() => throw new NotSupportedException();
///
public override int ReadByte()
@@ -186,10 +192,10 @@ namespace SixLabors.ImageSharp.Formats.Png.Zlib
if (disposing)
{
// dispose managed resources
- if (this.compressedStream != null)
+ if (this.CompressedStream != null)
{
- this.compressedStream.Dispose();
- this.compressedStream = null;
+ this.CompressedStream.Dispose();
+ this.CompressedStream = null;
}
}
@@ -264,7 +270,7 @@ namespace SixLabors.ImageSharp.Formats.Png.Zlib
}
// Initialize the deflate Stream.
- this.compressedStream = new DeflateStream(this, CompressionMode.Decompress, true);
+ this.CompressedStream = new DeflateStream(this, CompressionMode.Decompress, true);
return true;
}