public static void SetPPM(PNGFile aFile, uint aXPPM, uint aYPPM)
{
int pos = aFile.FindChunk(EPNGChunkType.pHYs);
PNGChunk chunk;
if (pos > 0)
{
chunk = aFile.chunks[pos];
if (chunk.data == null || chunk.data.Length < 9)
{
throw new System.Exception("PNG: pHYs chunk data size is too small. It should be at least 9 bytes");
}
}
else
{
chunk = new PNGChunk();
chunk.type = EPNGChunkType.pHYs;
chunk.length = 9;
chunk.data = new byte[9];
aFile.chunks.Insert(1, chunk); // insert right afrer IHDR
}
var data = chunk.data;
data[0] = (byte)((aXPPM >> 24) & 0xFF);
data[1] = (byte)((aXPPM >> 16) & 0xFF);
data[2] = (byte)((aXPPM >> 8) & 0xFF);
data[3] = (byte)((aXPPM) & 0xFF);
data[4] = (byte)((aYPPM >> 24) & 0xFF);
data[5] = (byte)((aYPPM >> 16) & 0xFF);
data[6] = (byte)((aYPPM >> 8) & 0xFF);
data[7] = (byte)((aYPPM) & 0xFF);
data[8] = 1;
chunk.crc = chunk.CalcCRC();
}
