/// <summary>
/// Reads the application extension block parsing any animation information
/// if present.
/// </summary>
private void ReadApplicationExtension()
{
int appLength = this.stream.ReadByte();
// If the length is 11 then it's a valid extension and most likely
// a NETSCAPE or ANIMEXTS extension. We want the loop count from this.
if (appLength == GifConstants.ApplicationBlockSize)
{
this.stream.Skip(appLength);
int subBlockSize = this.stream.ReadByte();
// TODO: There's also a NETSCAPE buffer extension.
// http://www.vurdalakov.net/misc/gif/netscape-buffering-application-extension
if (subBlockSize == GifConstants.NetscapeLoopingSubBlockSize)
{
this.stream.Read(this.buffer, 0, GifConstants.NetscapeLoopingSubBlockSize);
this.gifMetadata.RepeatCount = GifNetscapeLoopingApplicationExtension.Parse(this.buffer.AsSpan(1)).RepeatCount;
this.stream.Skip(1); // Skip the terminator.
return;
}
// Could be XMP or something else not supported yet.
// Skip the subblock and terminator.
this.SkipBlock(subBlockSize);
return;
}
this.SkipBlock(appLength); // Not supported by any known decoder.
}
/// <summary>
/// Reads the application extension block parsing any animation or XMP information
/// if present.
/// </summary>
private void ReadApplicationExtension()
{
int appLength = this.stream.ReadByte();
// If the length is 11 then it's a valid extension and most likely
// a NETSCAPE, XMP or ANIMEXTS extension. We want the loop count from this.
if (appLength == GifConstants.ApplicationBlockSize)
{
this.stream.Read(this.buffer, 0, GifConstants.ApplicationBlockSize);
bool isXmp = this.buffer.AsSpan().StartsWith(GifConstants.XmpApplicationIdentificationBytes);
if (isXmp && !this.IgnoreMetadata)
{
var extension = GifXmpApplicationExtension.Read(this.stream, this.MemoryAllocator);
if (extension.Data.Length > 0)
{
this.metadata.XmpProfile = new XmpProfile(extension.Data);
}
return;
}
else
{
int subBlockSize = this.stream.ReadByte();
// TODO: There's also a NETSCAPE buffer extension.
// http://www.vurdalakov.net/misc/gif/netscape-buffering-application-extension
if (subBlockSize == GifConstants.NetscapeLoopingSubBlockSize)
{
this.stream.Read(this.buffer, 0, GifConstants.NetscapeLoopingSubBlockSize);
this.gifMetadata.RepeatCount = GifNetscapeLoopingApplicationExtension.Parse(this.buffer.AsSpan(1)).RepeatCount;
this.stream.Skip(1); // Skip the terminator.
return;
}
// Could be something else not supported yet.
// Skip the subblock and terminator.
this.SkipBlock(subBlockSize);
}
return;
}
this.SkipBlock(appLength); // Not supported by any known decoder.
}
