示例#1
0
        public static void SetPPM(PNGFile aFile, uint aXPPM, uint aYPPM)
        {
            int      pos = aFile.FindChunk(EChunkType.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   = EChunkType.pHYs;
                chunk.length = 9;
                chunk.data   = new byte[9];
                aFile.chunks.Insert(1, chunk);
            }
            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();
        }