/// <summary>
/// Decodes the stream to the image.
/// </summary>
/// <typeparam name="TPixel">The pixel format.</typeparam>
/// <param name="stream">The stream containing image data. </param>
/// <exception cref="ImageFormatException">
/// Thrown if the stream does not contain and end chunk.
/// </exception>
/// <exception cref="System.ArgumentOutOfRangeException">
/// Thrown if the image is larger than the maximum allowable size.
/// </exception>
/// <returns>The decoded image</returns>
public Image <TPixel> Decode <TPixel>(Stream stream)
where TPixel : struct, IPixel <TPixel>
{
var metadata = new ImageMetaData();
this.currentStream = stream;
this.currentStream.Skip(8);
Image <TPixel> image = null;
PixelAccessor <TPixel> pixels = null;
try
{
using (var deframeStream = new ZlibInflateStream(this.currentStream))
{
PngChunk currentChunk;
while (!this.isEndChunkReached && (currentChunk = this.ReadChunk()) != null)
{
try
{
switch (currentChunk.Type)
{
case PngChunkTypes.Header:
this.ReadHeaderChunk(currentChunk.Data);
this.ValidateHeader();
break;
case PngChunkTypes.Physical:
this.ReadPhysicalChunk(metadata, currentChunk.Data);
break;
case PngChunkTypes.Data:
if (image == null)
{
this.InitializeImage(metadata, out image, out pixels);
}
deframeStream.AllocateNewBytes(currentChunk.Length);
this.ReadScanlines(deframeStream.CompressedStream, pixels);
stream.Read(this.crcBuffer, 0, 4);
break;
case PngChunkTypes.Palette:
byte[] pal = new byte[currentChunk.Length];
Buffer.BlockCopy(currentChunk.Data, 0, pal, 0, currentChunk.Length);
this.palette = pal;
metadata.Quality = pal.Length / 3;
break;
case PngChunkTypes.PaletteAlpha:
byte[] alpha = new byte[currentChunk.Length];
Buffer.BlockCopy(currentChunk.Data, 0, alpha, 0, currentChunk.Length);
this.paletteAlpha = alpha;
break;
case PngChunkTypes.Text:
this.ReadTextChunk(metadata, currentChunk.Data, currentChunk.Length);
break;
case PngChunkTypes.End:
this.isEndChunkReached = true;
break;
}
}
finally
{
// Data is rented in ReadChunkData()
if (currentChunk.Data != null)
{
ArrayPool <byte> .Shared.Return(currentChunk.Data);
}
}
}
}
return(image);
}
finally
{
pixels?.Dispose();
this.scanline?.Dispose();
this.previousScanline?.Dispose();
}
}