private void Handle_IDAT(PNGChunk chunk)
{
IDATChunk idatC = new IDATChunk();
idatC.ChunkData = chunk.ChunkData;
IDATList.Add(idatC);
}
static void Decode(ref PNG png)
{
Console.WriteLine($"\nDecoding zlib blocks...");
Stopwatch stopWatch = new Stopwatch();
stopWatch.Start();
uint idatLength = 0;
foreach (var chunk in png.IDATList)
{
idatLength += chunk.ChunkLength;
}
byte[] idatData = new byte[idatLength];
var offset = 0;
for (int i = 0; i < png.IDATList.Count(); i++)
{
Array.Copy(png.IDATList[i].ChunkData, 0, idatData, offset, (int)png.IDATList[i].ChunkLength);
offset += (int)png.IDATList[i].ChunkLength;
}
Stream idatStream = new MemoryStream(idatData);
var zlibHeader = new byte[2];
idatStream.Read(zlibHeader, 0, 2);
var bitBuffer = new byte[idatLength - 6]; // subtract 2 byte zlib header and 4 byte adler checksum.
idatStream.Read(bitBuffer, 0, (int)(idatLength - 6));
idatStream.Dispose();
BitArray bitArray = new BitArray(bitBuffer);
BitStream bs = new BitStream(bitArray);
bool lastBlock;
byte compression;
do
{
lastBlock = bs.GetNextBitsReverse(1) == 1;
compression = (byte)bs.GetNextBitsReverse(2);
if (compression == 0)
{
Console.WriteLine($"Zlib block already uncompressed...");
bs.GetNextBitsReverse(5);
ushort len = bs.GetNextShortReverse();
ushort nen = (ushort)~bs.GetNextShortReverse();
if (nen != len)
{
throw new Exception("Nen does not complement Len.");
}
for (int i = 0; i < len; i++)
{
bs.GetNextBitsReverse(8);
}
}
else if (compression == 1)
{
Console.WriteLine($"Uncompressing {(lastBlock ? "last " : "")}zlib block...");
Puff.ParseFixed(bs, lastBlock);
}
else if (compression == 2)
{
Console.WriteLine($"Uncompressing {(lastBlock ? "last " : "")}zlib block...");
Puff.ParseDynamic(bs, lastBlock);
}
}while (lastBlock == false);
if (compression != 0)
{
var adler = new Adler32();
adler.Update(bs.OutBuffer.ToArray());
byte[] adlerbytearray = BitConverter.GetBytes((int)adler.Value);
Array.Reverse(adlerbytearray, 0, adlerbytearray.Length);
Console.WriteLine($"Adler32 checksum = {adlerbytearray[0]} {adlerbytearray[1]} {adlerbytearray[2]} {adlerbytearray[3]}");
var numblocks = (bs.OutBuffer.Count()) / 65500;
var numblocksRem = (bs.OutBuffer.Count()) % 65500;
var splitBlocklist = new List <byte>();
if (numblocks > 0)
{
for (int j = 0; j < numblocks; j++)
{
InsertBlockHeader(splitBlocklist, 65500, false);
for (int i = 0; i < 65500; i++)
{
splitBlocklist.Add(bs.OutBuffer[i + j * 65500]);
}
}
InsertBlockHeader(splitBlocklist, (ushort)numblocksRem, true);
for (int i = (int)(bs.OutBuffer.Count() - numblocksRem); i < (bs.OutBuffer.Count()); i++)
{
splitBlocklist.Add(bs.OutBuffer[i]);
}
}
else
{
InsertBlockHeader(splitBlocklist, (ushort)numblocksRem, true);
for (int i = (int)(bs.OutBuffer.Count() - numblocksRem); i < (bs.OutBuffer.Count()); i++)
{
splitBlocklist.Add(bs.OutBuffer[i]);
}
}
for (int i = 0; i < adlerbytearray.Length; i++)
{
splitBlocklist.Add(adlerbytearray[i]);
}
byte[] newChunkData = new byte[splitBlocklist.Count() + 2];
zlibHeader.CopyTo(newChunkData, 0);
splitBlocklist.ToArray().CopyTo(newChunkData, 2);
var ncdChunks = newChunkData.Length / 65500;
var ncdRem = newChunkData.Length % 65500;
png.IDATList.Clear();
for (int i = 0; i < ncdChunks; i++)
{
IDATChunk newIdatChunk = new IDATChunk();
newIdatChunk.ChunkData = newChunkData.SubArray(i * 65500, 65500);
png.IDATList.Add(newIdatChunk);
}
IDATChunk finalIdatChunk = new IDATChunk();
finalIdatChunk.ChunkData = newChunkData.SubArray(newChunkData.Length - ncdRem, ncdRem);
png.IDATList.Add(finalIdatChunk);
}
stopWatch.Stop();
string elapsedTime = stopWatch.Elapsed.FormatTime();
Console.WriteLine($"Total decode time = {elapsedTime}");
}
