async Task ParseImageDescriptorAsync(GIFDecoderStreamReader stream, GIFBitmapDecoder decoder, GIFBitmap previousBitmap, bool ignoreImageData)
{
await ParseGIFBitmapHeaderAsync(stream).ConfigureAwait(false);
if (IsTransparent)
{
ColorTable.SetTransparency(TransparencyIndex);
}
DataPosition = stream.CurrentPosition;
if (!ignoreImageData)
{
// Decode LZW data stream.
await decoder.DecodeAsync(stream, _header.Width, _header.Height).ConfigureAwait(false);
// Compose bitmap from decoded data stream.
decoder.Compose(_header, this, previousBitmap);
// Consume block terminator.
await stream.SkipBlockAsync().ConfigureAwait(false);
}
else
{
// Read pass variable length LZW data stream.
// First byte is LZW code size followed by data blocks repeated until block terminator.
stream.Read();
await stream.SkipBlockAsync().ConfigureAwait(false);
}
if (IsTransparent)
{
ColorTable.ResetTransparency();
}
}
