/// <returns>Returns if this was the last chunk</returns>
public static bool GenerateChunk(NativeArray <byte> data, int length, ref Metadata metadata)
{
ChunkType?chunkType = null;
if (data[0] == 73 && data[1] == 72 && data[2] == 68 && data[3] == 82)
{
chunkType = ChunkType.IHDR;
}
else if (data[0] == 80 && data[1] == 76 && data[2] == 84 && data[3] == 69)
{
chunkType = ChunkType.PLTE;
}
else if (data[0] == 73 && data[1] == 68 && data[2] == 65 && data[3] == 84)
{
chunkType = ChunkType.IDAT;
}
else if (data[0] == 73 && data[1] == 69 && data[2] == 78 && data[3] == 68)
{
chunkType = ChunkType.IEND;
}
var isCriticalChunk = (data[0] & 32) == 0;
if (chunkType == null)
{
if (isCriticalChunk)
{
throw new NotImplementedException();
}
return(false);
}
//var isPublicChunk = (chunkTypeSpan[1] & 32) == 0;
//var isCompatiblePNGVersion = (chunkTypeSpan[2] & 32) == 0;
//var isSafeToCopy = (chunkTypeSpan[3] & 32) == 1;
// CRC
var expectedCRC = BitConverterBigEndian.ToUInt32(data.Slice(4 + length, 4));
var calculatedCRC = CRC32.Calculate(data.Slice(0, 4 + length));
Debug.Assert(expectedCRC == calculatedCRC, "CRC check failed. The data seems to be damaged.");
// Chunk Data
switch (chunkType)
{
case ChunkType.IHDR:
ReadIHDR(data.Slice(4, length), ref metadata);
return(false);
case ChunkType.IDAT:
metadata.Data.AddRange(data.GetSubArray(4, length)); // TODO Replace with a native array
return(false);
case ChunkType.IEND:
return(true);
default:
throw new Exception($"{nameof(chunkType)} matched no known types. Type was {GetASCIIString(data.Slice(0,4))}");
}
}
public void Execute()
{
//var fileStreamBuffer = FileData.Slice(0, 8);
// This signature indicates that the remainder of the datastream contains a single PNG image, consisting of a series of chunks beginning with an IHDR chunk and ending with an IEND chunk.
//Debug.Assert(fileStreamBuffer.SequenceEqual(pngSignature), "This doesn't seem to be a PNG");
bool lastChunk;
var metadata = new Metadata(FileData.Length);
var offset = 8;
do
{
var length = BitConverterBigEndian.ToUInt32(FileData.Slice(offset, 4));
var signedLength = checked ((int)length);
lastChunk = ChunkGenerator.GenerateChunk(FileData.GetSubArray(offset + 4, signedLength + 8), signedLength, ref metadata);
offset += 12 + signedLength;
} while (!lastChunk);
//var tmpScanlineColor = new Color32[metadata.Width];
NativeArray <byte> uncompressedData;
var metadataData = metadata.Data;
var buffer = metadataData.ToArray();
using (var zlibStream = new ZlibStream(new MemoryStream(buffer), Ionic.Zlib.CompressionMode.Decompress)) {
using (var memoryStream = new MemoryStream()) {
zlibStream.CopyTo(memoryStream);
uncompressedData = new NativeArray <byte>(memoryStream.ToArray(), Allocator.Temp);
}
}
Debug.Assert(uncompressedData.Length >= 1);
int bytesPerPixel;
switch (metadata.ColourType)
{
case Metadata.ColourTypeEnum.GREYSCALE:
bytesPerPixel = 1;
throw new NotImplementedException();
case Metadata.ColourTypeEnum.TRUECOLOUR:
bytesPerPixel = 3;
break;
case Metadata.ColourTypeEnum.INDEXED_COLOUR:
bytesPerPixel = 1;
throw new NotImplementedException();
case Metadata.ColourTypeEnum.GREYSCALE_WITH_ALPHA:
bytesPerPixel = 2;
throw new NotImplementedException();
case Metadata.ColourTypeEnum.TRUECOLOUR_WITH_ALPHA:
bytesPerPixel = 4;
break;
default:
throw new ArgumentOutOfRangeException();
}
Width[0] = checked ((int)metadata.Width);
Height[0] = checked ((int)metadata.Height);
RawTextureData.Resize(Width[0] * Height[0] * 4, NativeArrayOptions.UninitializedMemory);
for (var aktLine = 0; aktLine < metadata.Height; aktLine++)
{
var firstRowBytePosition = aktLine * (Width[0] * bytesPerPixel + 1);
//Color32[] lineColors = null;
switch ((FilterType)uncompressedData[firstRowBytePosition])
{
case FilterType.NONE:
break;
case FilterType.SUB:
FilterLineSub(ref uncompressedData, firstRowBytePosition, Width[0], bytesPerPixel);
break;
case FilterType.UP:
FilterLineUp(ref uncompressedData, firstRowBytePosition, Width[0], bytesPerPixel);
break;
case FilterType.AVERAGE:
FilterLineAverage(ref uncompressedData, firstRowBytePosition, Width[0], bytesPerPixel);
break;
case FilterType.PAETH:
FilterLinePaeth(ref uncompressedData, firstRowBytePosition, Width[0], bytesPerPixel);
break;
default:
throw new ArgumentOutOfRangeException();
}
for (var i = 0; i < Width[0]; i++)
{
RawTextureData[(int)((metadata.Height - 1 - aktLine) * metadata.Width * 4 + i * 4)] = uncompressedData[firstRowBytePosition + 1 + i * bytesPerPixel];
RawTextureData[(int)((metadata.Height - 1 - aktLine) * metadata.Width * 4 + i * 4 + 1)] = uncompressedData[firstRowBytePosition + 2 + i * bytesPerPixel];
RawTextureData[(int)((metadata.Height - 1 - aktLine) * metadata.Width * 4 + i * 4 + 2)] = uncompressedData[firstRowBytePosition + 3 + i * bytesPerPixel];
RawTextureData[(int)((metadata.Height - 1 - aktLine) * metadata.Width * 4 + i * 4 + 3)] = bytesPerPixel == 4 ? uncompressedData[firstRowBytePosition + 4 + i * bytesPerPixel] : byte.MaxValue;
}
}
}