private void DisposePreviousFrame(GifFrame currentFrame)
{
GifFrame previousFrame = this._previousFrame;
GifGraphicControlExtension controlExtension = previousFrame != null ? previousFrame.GraphicControl : null;
if (controlExtension != null)
{
switch (controlExtension.DisposalMethod)
{
case GifFrameDisposalMethod.RestoreBackground:
this.ClearArea((IGifRect)this._previousFrame.Descriptor);
break;
case GifFrameDisposalMethod.RestorePrevious:
Animator.CopyToBitmap(this._previousBackBuffer, this._bitmap, 0, this._previousBackBuffer.Length);
break;
}
}
GifGraphicControlExtension graphicControl = currentFrame.GraphicControl;
if (graphicControl == null || graphicControl.DisposalMethod != GifFrameDisposalMethod.RestorePrevious)
{
return;
}
Animator.CopyFromBitmap(this._previousBackBuffer, this._bitmap, 0, this._previousBackBuffer.Length);
}
private void ClearArea(IGifRect rect)
{
int length = 4 * rect.Width;
byte[] buffer = new byte[length];
for (int index = 0; index < rect.Height; ++index)
{
int offset = (rect.Top + index) * this._stride + 4 * rect.Left;
Animator.CopyToBitmap(buffer, this._bitmap, offset, length);
}
}
private async Task RenderFrameAsync(int frameIndex, CancellationToken cancellationToken)
{
if (frameIndex < 0)
{
return;
}
GifFrame frame = this._metadata.Frames[frameIndex];
GifImageDescriptor desc = frame.Descriptor;
using (Stream indexStreamAsync = await this.GetIndexStreamAsync(frame, cancellationToken))
{
if (frameIndex < this._previousFrameIndex)
{
this.ClearArea((IGifRect)this._metadata.Header.LogicalScreenDescriptor);
}
else
{
this.DisposePreviousFrame(frame);
}
int length = 4 * desc.Width;
byte[] buffer = new byte[desc.Width];
byte[] numArray = new byte[length];
Animator.GifPalette palette = this._palettes[frameIndex];
int num1 = palette.TransparencyIndex ?? -1;
foreach (int num2 in frame.Descriptor.Interlace ? Animator.InterlacedRows(frame.Descriptor.Height) : Animator.NormalRows(frame.Descriptor.Height))
{
if (indexStreamAsync.Read(buffer, 0, desc.Width) != desc.Width)
{
throw new EndOfStreamException();
}
int offset = (desc.Top + num2) * this._stride + desc.Left * 4;
if (num1 >= 0)
{
Animator.CopyFromBitmap(numArray, this._bitmap, offset, length);
}
for (int index = 0; index < desc.Width; ++index)
{
byte num3 = buffer[index];
int startIndex = 4 * index;
if ((int)num3 != num1)
{
Animator.WriteColor(numArray, palette[(int)num3], startIndex);
}
}
Animator.CopyToBitmap(numArray, this._bitmap, offset, length);
}
this._bitmap.Invalidate();
this._previousFrame = frame;
this._previousFrameIndex = frameIndex;
}
}
