static public PNG_IHDR FromBytes(byte[] bytes)
{
int size = Marshal.SizeOf(typeof(PNG_IHDR));
IntPtr ptr = Marshal.AllocHGlobal(size);
Marshal.Copy(bytes, 0, ptr, size);
PNG_IHDR result = (PNG_IHDR)Marshal.PtrToStructure(ptr, typeof(PNG_IHDR));
Marshal.FreeHGlobal(ptr);
result.Width = IPAddress.HostToNetworkOrder(result.Width);
result.Height = IPAddress.HostToNetworkOrder(result.Height);
return(result);
}
static PNG_Chunk[] ProcessChunks(PNG_Chunk[] chunks)
{
List <PNG_Chunk> result = new List <PNG_Chunk>();
PNG_IHDR header = new PNG_IHDR();
using (MemoryStream rawData = new MemoryStream())
{
foreach (PNG_Chunk chunk in chunks)
{
if (chunk.Name.Equals(PNG_CgBIChunk))
{
continue;
}
if (chunk.Name.Equals(PNG_HeaderChunk))
{
header = PNG_IHDR.FromBytes(chunk.Data);
}
if (chunk.Name.Equals(PNG_DataChunk))
{
rawData.Write(chunk.Data, 0, chunk.Data.Length);
continue;
}
if (chunk.Name.Equals(PNG_EndChunk))
{
const int dataChunkSize = 16 * 1024;
rawData.Position = 0;
using (MemoryStream buffer = new MemoryStream())
{
using (InflaterInputStream inflate = new InflaterInputStream(rawData, new Inflater(true)))
{
inflate.IsStreamOwner = false;
IPATools.Utilities.Utils.CopyStream(inflate, buffer);
//inflate.CopyTo(buffer);
}
buffer.Position = 0;
rawData.SetLength(0);
IPATools.Utilities.Utils.CopyStream(buffer, rawData);
//buffer.CopyTo(rawData);
}
{
byte[] imageData = rawData.GetBuffer();
int scanlineSize = header.Width * 4 + 1;
int scanlinePos = 0;
int bpp = 4;
for (int y = 0; y < header.Height; ++y, scanlinePos += scanlineSize)
{
PNG_Filter filter = (PNG_Filter)imageData[scanlinePos];
switch (filter)
{
case PNG_Filter.Sub:
for (int x = 1 + bpp; x < scanlineSize; ++x)
{
imageData[scanlinePos + x] = (byte)((int)imageData[scanlinePos + x] + (int)imageData[scanlinePos + x - bpp]);
}
break;
case PNG_Filter.Up:
if (y > 0)
{
for (int x = 1; x < scanlineSize; ++x)
{
imageData[scanlinePos + x] = (byte)((int)imageData[scanlinePos + x] + (int)imageData[scanlinePos + x - bpp - scanlineSize]);
}
}
break;
case PNG_Filter.Average:
if (y > 0)
{
for (int x = 1 + bpp; x < scanlineSize; ++x)
{
imageData[scanlinePos + x] = (byte)
(((int)imageData[scanlinePos + x - bpp] +
(int)imageData[scanlinePos + x - bpp - scanlineSize]) >> 1);
}
}
break;
case PNG_Filter.Paeth:
if (y > 0)
{
for (int x = 1 + bpp; x < scanlineSize; ++x)
{
imageData[scanlinePos + x] =
(byte)FilterPaethPredictor(
imageData[scanlinePos + x - bpp],
imageData[scanlinePos + x - bpp - scanlineSize],
imageData[scanlinePos + x - scanlineSize]);
}
}
break;
}
for (int x = 0; x < header.Width; ++x)
{
byte r = imageData[scanlinePos + x * 4 + 1];
byte g = imageData[scanlinePos + x * 4 + 2];
byte b = imageData[scanlinePos + x * 4 + 3];
byte a = imageData[scanlinePos + x * 4 + 4];
if (a > 0)
{
r = (byte)(255 * r / a);
g = (byte)(255 * g / a);
b = (byte)(255 * b / a);
}
imageData[scanlinePos + x * 4 + 1] = b;
imageData[scanlinePos + x * 4 + 2] = g;
imageData[scanlinePos + x * 4 + 3] = r;
imageData[scanlinePos + x * 4 + 4] = a;
}
imageData[scanlinePos] = (byte)PNG_Filter.None;
//imageData[scanlinePos] = (byte)PNG_Filter.Sub;
//for (int x = 1 + bpp; x < scanlineSize; ++x)
//{
// byte c = imageData[scanlinePos + x];
// byte l = imageData[scanlinePos + x - bpp];
// imageData[scanlinePos + x] = (byte)(l - c);
//}
}
}
Deflater deflater = new Deflater(9);
Crc32 crc32 = new Crc32();
rawData.Position = 0;
long dataLeft = rawData.Length;
while (dataLeft > 0)
{
byte[] chunkData = new byte[dataChunkSize];
int dataInChunk = rawData.Read(chunkData, 0, dataChunkSize);
dataLeft -= dataInChunk;
byte[] deflatedChunkData = new byte[dataChunkSize];
deflater.SetInput(chunkData, 0, dataInChunk);
if (dataLeft > 0)
{
deflater.Flush();
}
else
{
deflater.Finish();
}
int deflatedBytes = deflater.Deflate(deflatedChunkData, 0, dataInChunk);
PNG_Chunk dataChunk = new PNG_Chunk();
dataChunk.Name = PNG_DataChunk;
dataChunk.Data = new byte[deflatedBytes];
for (int i = 0; i < deflatedBytes; ++i)
{
dataChunk.Data[i] = deflatedChunkData[i];
}
crc32.Reset();
crc32.Update(ASCIIEncoding.ASCII.GetBytes(dataChunk.Name));
crc32.Update(dataChunk.Data);
dataChunk.CRC = (uint)crc32.Value;
result.Add(dataChunk);
}
}
result.Add(chunk);
}
}
return(result.ToArray());
}
