internal bool ReadFrames()
{
//Png header, 8 bytes.
if (!InternalStream.ReadBytes(8).SequenceEqual(new byte[] { 137, 80, 78, 71, 13, 10, 26, 10 }))
{
throw new Exception("Invalid file format, expected PNG signature not found.");
}
//IHDR chunk, 25 bytes.
Ihdr = IhdrChunk.Read(InternalStream);
//aCTl chunk, 16 bytes.
Actl = ActlChunk.Read(InternalStream);
//If there's no animation control chunk, it's a normal Png.
if (Actl == null)
{
return(false);
}
var masterSequence = 0;
var frameGroupId = -1;
//Read frames.
while (InternalStream.CanRead)
{
//Tries to read any chunk, except IEND.
var chunk = Chunk.Read(InternalStream, masterSequence++);
//End reached, prematurely or not.
if (chunk == null || chunk.ChunkType == "IEND")
{
break;
}
//Chunks can be grouped into frames.
if (new[] { "fcTL", "fdAT", "IDAT" }.Contains(chunk.ChunkType))
{
if (chunk.ChunkType == "fcTL")
{
frameGroupId++;
}
chunk.FrameGroupId = frameGroupId;
}
Chunks.Add(chunk);
}
return(true);
}
