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Apply Otimizations to gif decoder. Touch #54

af/merge-core
James Jackson-South 9 years ago
parent
43996c4399
commit
b89d96e07b
2 changed files with 127 additions and 101 deletions
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  1. 226
      src/ImageSharp/Formats/Gif/GifDecoderCore.cs
  2. 2
      src/ImageSharp/Formats/Gif/GifEncoderCore.cs

226
src/ImageSharp/Formats/Gif/GifDecoderCore.cs
View File

@ -6,6 +6,7 @@
namespace ImageSharp.Formats
{
using System;
using System.Buffers;
using System.IO;
/// <summary>
@ -17,6 +18,11 @@ namespace ImageSharp.Formats
where TColor : struct, IPackedPixel<TPacked>
where TPacked : struct, IEquatable<TPacked>
{
/// <summary>
/// The temp buffer used to reduce allocations.
/// </summary>
private readonly byte[] buffer = new byte[16];
/// <summary>
/// The image to decode the information to.
/// </summary>
@ -32,6 +38,11 @@ namespace ImageSharp.Formats
/// </summary>
private byte[] globalColorTable;
/// <summary>
/// The global color table length
/// </summary>
private int globalColorTableLength;
/// <summary>
/// The current frame.
/// </summary>
@ -54,55 +65,65 @@ namespace ImageSharp.Formats
/// <param name="stream">The stream containing image data. </param>
public void Decode(Image<TColor, TPacked> image, Stream stream)
{
this.decodedImage = image;
this.currentStream = stream;
// Skip the identifier
this.currentStream.Skip(6);
this.ReadLogicalScreenDescriptor();
if (this.logicalScreenDescriptor.GlobalColorTableFlag)
try
{
this.globalColorTable = new byte[this.logicalScreenDescriptor.GlobalColorTableSize * 3];
this.decodedImage = image;
this.currentStream = stream;
// Read the global color table from the stream
stream.Read(this.globalColorTable, 0, this.globalColorTable.Length);
}
// Skip the identifier
this.currentStream.Skip(6);
this.ReadLogicalScreenDescriptor();
// Loop though the respective gif parts and read the data.
int nextFlag = stream.ReadByte();
while (nextFlag != GifConstants.Terminator)
{
if (nextFlag == GifConstants.ImageLabel)
if (this.logicalScreenDescriptor.GlobalColorTableFlag)
{
this.ReadFrame();
this.globalColorTableLength = this.logicalScreenDescriptor.GlobalColorTableSize * 3;
this.globalColorTable = ArrayPool<byte>.Shared.Rent(this.globalColorTableLength);
// Read the global color table from the stream
stream.Read(this.globalColorTable, 0, this.globalColorTableLength);
}
else if (nextFlag == GifConstants.ExtensionIntroducer)
// Loop though the respective gif parts and read the data.
int nextFlag = stream.ReadByte();
while (nextFlag != GifConstants.Terminator)
{
int label = stream.ReadByte();
switch (label)
if (nextFlag == GifConstants.ImageLabel)
{
case GifConstants.GraphicControlLabel:
this.ReadGraphicalControlExtension();
break;
case GifConstants.CommentLabel:
this.ReadComments();
break;
case GifConstants.ApplicationExtensionLabel:
this.Skip(12); // No need to read.
break;
case GifConstants.PlainTextLabel:
this.Skip(13); // Not supported by any known decoder.
break;
this.ReadFrame();
}
else if (nextFlag == GifConstants.ExtensionIntroducer)
{
int label = stream.ReadByte();
switch (label)
{
case GifConstants.GraphicControlLabel:
this.ReadGraphicalControlExtension();
break;
case GifConstants.CommentLabel:
this.ReadComments();
break;
case GifConstants.ApplicationExtensionLabel:
this.Skip(12); // No need to read.
break;
case GifConstants.PlainTextLabel:
this.Skip(13); // Not supported by any known decoder.
break;
}
}
else if (nextFlag == GifConstants.EndIntroducer)
{
break;
}
nextFlag = stream.ReadByte();
}
else if (nextFlag == GifConstants.EndIntroducer)
}
finally
{
if (this.globalColorTable != null)
{
break;
ArrayPool<byte>.Shared.Return(this.globalColorTable);
}
nextFlag = stream.ReadByte();
}
}
@ -111,16 +132,14 @@ namespace ImageSharp.Formats
/// </summary>
private void ReadGraphicalControlExtension()
{
byte[] buffer = new byte[6];
this.currentStream.Read(buffer, 0, buffer.Length);
this.currentStream.Read(this.buffer, 0, 6);
byte packed = buffer[1];
byte packed = this.buffer[1];
this.graphicsControlExtension = new GifGraphicsControlExtension
{
DelayTime = BitConverter.ToInt16(buffer, 2),
TransparencyIndex = buffer[4],
DelayTime = BitConverter.ToInt16(this.buffer, 2),
TransparencyIndex = this.buffer[4],
TransparencyFlag = (packed & 0x01) == 1,
DisposalMethod = (DisposalMethod)((packed & 0x1C) >> 2)
};
@ -132,18 +151,16 @@ namespace ImageSharp.Formats
/// <returns><see cref="GifImageDescriptor"/></returns>
private GifImageDescriptor ReadImageDescriptor()
{
byte[] buffer = new byte[9];
this.currentStream.Read(this.buffer, 0, 9);
this.currentStream.Read(buffer, 0, buffer.Length);
byte packed = buffer[8];
byte packed = this.buffer[8];
GifImageDescriptor imageDescriptor = new GifImageDescriptor
{
Left = BitConverter.ToInt16(buffer, 0),
Top = BitConverter.ToInt16(buffer, 2),
Width = BitConverter.ToInt16(buffer, 4),
Height = BitConverter.ToInt16(buffer, 6),
Left = BitConverter.ToInt16(this.buffer, 0),
Top = BitConverter.ToInt16(this.buffer, 2),
Width = BitConverter.ToInt16(this.buffer, 4),
Height = BitConverter.ToInt16(this.buffer, 6),
LocalColorTableFlag = ((packed & 0x80) >> 7) == 1,
LocalColorTableSize = 2 << (packed & 0x07),
InterlaceFlag = ((packed & 0x40) >> 6) == 1
@ -157,26 +174,23 @@ namespace ImageSharp.Formats
/// </summary>
private void ReadLogicalScreenDescriptor()
{
byte[] buffer = new byte[7];
this.currentStream.Read(buffer, 0, buffer.Length);
this.currentStream.Read(this.buffer, 0, 7);
byte packed = buffer[4];
byte packed = this.buffer[4];
this.logicalScreenDescriptor = new GifLogicalScreenDescriptor
{
Width = BitConverter.ToInt16(buffer, 0),
Height = BitConverter.ToInt16(buffer, 2),
BackgroundColorIndex = buffer[5],
PixelAspectRatio = buffer[6],
Width = BitConverter.ToInt16(this.buffer, 0),
Height = BitConverter.ToInt16(this.buffer, 2),
BackgroundColorIndex = this.buffer[5],
PixelAspectRatio = this.buffer[6],
GlobalColorTableFlag = ((packed & 0x80) >> 7) == 1,
GlobalColorTableSize = 2 << (packed & 0x07)
};
if (this.logicalScreenDescriptor.GlobalColorTableSize > 255 * 4)
{
throw new ImageFormatException(
$"Invalid gif colormap size '{this.logicalScreenDescriptor.GlobalColorTableSize}'");
throw new ImageFormatException($"Invalid gif colormap size '{this.logicalScreenDescriptor.GlobalColorTableSize}'");
}
if (this.logicalScreenDescriptor.Width > this.decodedImage.MaxWidth || this.logicalScreenDescriptor.Height > this.decodedImage.MaxHeight)
@ -216,11 +230,17 @@ namespace ImageSharp.Formats
throw new ImageFormatException($"Gif comment length '{flag}' exceeds max '{GifConstants.MaxCommentLength}'");
}
byte[] buffer = new byte[flag];
this.currentStream.Read(buffer, 0, flag);
byte[] flagBuffer = ArrayPool<byte>.Shared.Rent(flag);
this.decodedImage.Properties.Add(new ImageProperty("Comments", BitConverter.ToString(buffer)));
try
{
this.currentStream.Read(flagBuffer, 0, flag);
this.decodedImage.Properties.Add(new ImageProperty("Comments", BitConverter.ToString(flagBuffer, 0, flag)));
}
finally
{
ArrayPool<byte>.Shared.Return(flagBuffer);
}
}
}
@ -231,18 +251,32 @@ namespace ImageSharp.Formats
{
GifImageDescriptor imageDescriptor = this.ReadImageDescriptor();
byte[] localColorTable = this.ReadFrameLocalColorTable(imageDescriptor);
byte[] indices = this.ReadFrameIndices(imageDescriptor);
byte[] localColorTable = null;
// Determine the color table for this frame. If there is a local one, use it
// otherwise use the global color table.
byte[] colorTable = localColorTable ?? this.globalColorTable;
try
{
// Determine the color table for this frame. If there is a local one, use it otherwise use the global color table.
int length = this.globalColorTableLength;
if (imageDescriptor.LocalColorTableFlag)
{
length = imageDescriptor.LocalColorTableSize * 3;
localColorTable = ArrayPool<byte>.Shared.Rent(length);
this.currentStream.Read(localColorTable, 0, length);
}
this.ReadFrameColors(indices, colorTable, imageDescriptor);
byte[] indices = this.ReadFrameIndices(imageDescriptor);
this.ReadFrameColors(indices, localColorTable ?? this.globalColorTable, length, imageDescriptor);
// Skip any remaining blocks
this.Skip(0);
// Skip any remaining blocks
this.Skip(0);
}
finally
{
if (localColorTable != null)
{
ArrayPool<byte>.Shared.Return(localColorTable);
}
}
}
/// <summary>
@ -259,32 +293,14 @@ namespace ImageSharp.Formats
}
}
/// <summary>
/// Reads the local color table from the current frame.
/// </summary>
/// <param name="imageDescriptor">The <see cref="GifImageDescriptor"/>.</param>
/// <returns>The <see cref="T:byte[]"/></returns>
private byte[] ReadFrameLocalColorTable(GifImageDescriptor imageDescriptor)
{
byte[] localColorTable = null;
if (imageDescriptor.LocalColorTableFlag)
{
localColorTable = new byte[imageDescriptor.LocalColorTableSize * 3];
this.currentStream.Read(localColorTable, 0, localColorTable.Length);
}
return localColorTable;
}
/// <summary>
/// Reads the frames colors, mapping indices to colors.
/// </summary>
/// <param name="indices">The indexed pixels.</param>
/// <param name="colorTable">The color table containing the available colors.</param>
/// <param name="colorTableLength">The color table length.</param>
/// <param name="descriptor">The <see cref="GifImageDescriptor"/></param>
private void ReadFrameColors(byte[] indices, byte[] colorTable, GifImageDescriptor descriptor)
private void ReadFrameColors(byte[] indices, byte[] colorTable, int colorTableLength, GifImageDescriptor descriptor)
{
int imageWidth = this.logicalScreenDescriptor.Width;
int imageHeight = this.logicalScreenDescriptor.Height;
@ -301,7 +317,12 @@ namespace ImageSharp.Formats
{
lastFrame = new TColor[imageWidth * imageHeight];
Array.Copy(this.currentFrame, lastFrame, lastFrame.Length);
// Array.Copy(this.currentFrame, lastFrame, lastFrame.Length);
using (PixelAccessor<TColor, TPacked> lastPixels = lastFrame.Lock<TColor, TPacked>(imageWidth, imageHeight))
using (PixelAccessor<TColor, TPacked> currentPixels = this.currentFrame.Lock<TColor, TPacked>(imageWidth, imageHeight))
{
currentPixels.CopyImage(lastPixels);
}
}
int offset, i = 0;
@ -368,7 +389,12 @@ namespace ImageSharp.Formats
TColor[] pixels = new TColor[imageWidth * imageHeight];
Array.Copy(this.currentFrame, pixels, pixels.Length);
// Array.Copy(this.currentFrame, pixels, pixels.Length);
using (PixelAccessor<TColor, TPacked> newPixels = pixels.Lock<TColor, TPacked>(imageWidth, imageHeight))
using (PixelAccessor<TColor, TPacked> currentPixels = this.currentFrame.Lock<TColor, TPacked>(imageWidth, imageHeight))
{
currentPixels.CopyImage(newPixels);
}
ImageBase<TColor, TPacked> currentImage;
@ -376,7 +402,7 @@ namespace ImageSharp.Formats
{
currentImage = this.decodedImage;
currentImage.SetPixels(imageWidth, imageHeight, pixels);
currentImage.Quality = colorTable.Length / 3;
currentImage.Quality = colorTableLength / 3;
if (this.graphicsControlExtension != null && this.graphicsControlExtension.DelayTime > 0)
{
@ -389,7 +415,7 @@ namespace ImageSharp.Formats
currentImage = frame;
currentImage.SetPixels(imageWidth, imageHeight, pixels);
currentImage.Quality = colorTable.Length / 3;
currentImage.Quality = colorTableLength / 3;
if (this.graphicsControlExtension != null && this.graphicsControlExtension.DelayTime > 0)
{
@ -421,4 +447,4 @@ namespace ImageSharp.Formats
}
}
}
}
}

2
src/ImageSharp/Formats/Gif/GifEncoderCore.cs
View File

@ -19,7 +19,7 @@ namespace ImageSharp.Formats
internal sealed class GifEncoderCore
{
/// <summary>
/// The pixel buffer, used to reduce allocations.
/// The temp buffer used to reduce allocations.
/// </summary>
private readonly byte[] buffer = new byte[16];

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