private async Task<Stream> GetIndexStreamAsync(GifFrame frame, CancellationToken cancellationToken)
{
var data = frame.ImageData;
cancellationToken.ThrowIfCancellationRequested();
_sourceStream.Seek(data.CompressedDataStartOffset, SeekOrigin.Begin);
using (var ms = new MemoryStream(_indexStreamBuffer))
{
await GifHelpers.CopyDataBlocksToStreamAsync(_sourceStream, ms, cancellationToken).ConfigureAwait(false);
}
var lzwStream = new LzwDecompressStream(_indexStreamBuffer, data.LzwMinimumCodeSize);
return lzwStream;
}
private static async Task DecompressAllFramesAsync(string path)
{
using var fileStream = File.OpenRead(path);
var gif = await GifDataStream.ReadAsync(fileStream);
for (int i = 0; i < gif.Frames.Count; i++)
{
var frame = gif.Frames[i];
fileStream.Seek(frame.ImageData.CompressedDataStartOffset, SeekOrigin.Begin);
using var ms = new MemoryStream();
await GifHelpers.CopyDataBlocksToStreamAsync(fileStream, ms);
using var lzwStream = new LzwDecompressStream(ms.GetBuffer(), frame.ImageData.LzwMinimumCodeSize);
using var indOutStream = File.OpenWrite($"{path}.{i}.ind");
await lzwStream.CopyToAsync(indOutStream);
}
}
private static async Task TestLzwDecompressionAsync(string path)
{
using (var fileStream = File.OpenRead(path))
{
var gif = await GifDataStream.ReadAsync(fileStream);
var firstFrame = gif.Frames[0];
fileStream.Seek(firstFrame.ImageData.CompressedDataStartOffset, SeekOrigin.Begin);
using (var ms = new MemoryStream())
{
await GifHelpers.CopyDataBlocksToStreamAsync(fileStream, ms);
using (var lzwStream = new LzwDecompressStream(ms.GetBuffer(), firstFrame.ImageData.LzwMinimumCodeSize))
using (var indOutStream = File.OpenWrite(path + ".ind"))
{
await lzwStream.CopyToAsync(indOutStream);
}
}
}
}
