/// <summary>
/// Creates an FDAT Chunk from an IDAT Chunk.
/// </summary>
/// <returns>The FDAT chunk.</returns>
/// <param name="idatChunk">IDAT chunk.</param>
/// <param name="sequenceNumber">Sequence number.</param>
public static fdATChunk FromIDATChunk(IDATChunk idatChunk, uint sequenceNumber)
{
uint newCrc;
byte[] frameData;
fdATChunk fdat = null;
using (var msCrc = new MemoryStream())
{
msCrc.WriteBytes(new[] { (byte)'f', (byte)'d', (byte)'A', (byte)'T' });
byte[] seqNum = BitConverter.GetBytes(Helper.ConvertEndian(sequenceNumber));
frameData = new byte[seqNum.Length + idatChunk.ChunkData.Length];
Buffer.BlockCopy(seqNum, 0, frameData, 0, seqNum.Length);
Buffer.BlockCopy(idatChunk.ChunkData, 0, frameData, seqNum.Length, idatChunk.ChunkData.Length);
msCrc.WriteBytes(frameData);
newCrc = CrcHelper.Calculate(msCrc.ToArray());
}
using (var ms = new MemoryStream())
{
ms.WriteUInt32((uint)Helper.ConvertEndian(idatChunk.ChunkData.Length + 4));
ms.WriteBytes(new[] { (byte)'f', (byte)'d', (byte)'A', (byte)'T' });
ms.WriteBytes(frameData);
ms.WriteUInt32(Helper.ConvertEndian(newCrc));
ms.Position = 0;
fdat = new fdATChunk(ms);
}
return(fdat);
}
/// <summary>
/// Save the APNG to file.
/// </summary>
/// <param name="filename">The filename to output to.</param>
public void Save(string filename)
{
using (BinaryWriter writer = new BinaryWriter(new FileStream(filename, FileMode.OpenOrCreate, FileAccess.Write)))
{
int frameWriteStartIndex = 0;
//Write signature
writer.Write(Frame.Signature);
//Write header
writer.Write(this.IHDRChunk.RawData);
//If acTL exists
if (acTLChunk != null)
{
//write actl.
writer.Write(acTLChunk.RawData);
}
//Write all other chunks. (NOTE: These should be consistently the same for all frames)
foreach (OtherChunk otherChunk in defaultImage.OtherChunks)
{
writer.Write(otherChunk.RawData);
}
uint sequenceNumber = 0;
//If Default Image is not animated
if (!DefaultImageIsAnimated)
{
//write IDAT
defaultImage.IDATChunks.ForEach(i => writer.Write(i.RawData));
}
else
{
frames[0].fcTLChunk.SequenceNumber = sequenceNumber++;
//Write fcTL
writer.Write(frames[0].fcTLChunk.RawData);
//Write IDAT of first frame.
frames[0].IDATChunks.ForEach(i => writer.Write(i.RawData));
//Set start frame indes to 1
frameWriteStartIndex = 1;
}
//Foreach frame
for (int i = frameWriteStartIndex; i < frames.Count; ++i)
{
frames[i].fcTLChunk.SequenceNumber = sequenceNumber++;
//write fcTL
writer.Write(frames[i].fcTLChunk.RawData);
//Write fDAT
for (int j = 0; j < frames[i].IDATChunks.Count; ++j)
{
fdATChunk fdat = fdATChunk.FromIDATChunk(frames[i].IDATChunks[j], sequenceNumber++);
writer.Write(fdat.RawData);
}
}
//Write IEnd
writer.Write(defaultImage.IENDChunk.RawData);
writer.Close();
}
}
