async Task ParseAsync(GIFDecoderStreamReader stream, bool skipTypeIdentifier)
{
if (!skipTypeIdentifier)
{
TypeIdentifier = stream.ReadString(3);
}
else
{
TypeIdentifier = "GIF";
}
if (IsGIFHeader)
{
Version = stream.ReadString(3);
Width = stream.ReadShort();
Height = stream.ReadShort();
int flags = stream.Read();
BackgroundColorIndex = stream.Read();
PixelAspectRatio = stream.Read();
if (UseGlobalColorTable(flags))
{
GlobalColorTable = await GIFColorTable.CreateColorTableAsync(stream, GlobalColorTableSize(flags)).ConfigureAwait(false);
BackgroundColor = GlobalColorTable.Data[BackgroundColorIndex];
}
}
else
{
throw new GIFDecoderFormatException("Unknown GIF format type identifier: " + TypeIdentifier);
}
}
async Task ParseGIFBitmapHeaderAsync(GIFDecoderStreamReader stream)
{
Bounds = new GIFBitmap.Rect(stream.ReadShort(), stream.ReadShort(), stream.ReadShort(), stream.ReadShort());
ColorTable = _header.GlobalColorTable;
int flags = stream.Read();
if (UseLocalColorTable(flags))
{
ColorTable = await GIFColorTable.CreateColorTableAsync(stream, LocalColorTableSize(flags)).ConfigureAwait(false);
}
BackgroundColor = _header.BackgroundColor;
IsInterlaced = UseInterlace(flags);
}
void ParseGraphicControlExtension(GIFDecoderStreamReader stream)
{
int blockSize = stream.Read();
if (blockSize != 4)
{
throw new GIFDecoderFormatException("Invalid graphic control extension size.");
}
int flags = stream.Read();
SetDisposeMethod(flags);
SetDelay(stream.ReadShort());
SetTransparency(flags, stream.Read());
// Consume block terminator.
stream.Read();
}