private bool ApplyChunkIHDR(byte[] dataArray)
{
// verify length
if (13 != dataArray.Length)
{
return(false);
}
byte[] sizeArray = new byte[4];
Array.Copy(dataArray, 0, sizeArray, 0, 4);
width = PNGUtil.GetInt(sizeArray);
Array.Copy(dataArray, 4, sizeArray, 0, 4);
height = PNGUtil.GetInt(sizeArray);
bitDepth = (int)dataArray[8];
colorType = (int)dataArray[9];
compressMethod = (int)dataArray[10];
filterMethod = (int)dataArray[11];
interlaceMethod = (int)dataArray[12];
if (bitDepth != 8)
{
errorMessage = "can't handle bit depth " + bitDepth;
return(false);
}
if (colorType != 2)
{
errorMessage = "can't handle color type " + colorType;
return(false);
}
if (compressMethod != 0)
{
errorMessage = "strange compress method " + compressMethod;
return(false);
}
if (filterMethod != 0)
{
errorMessage = "strange filter method " + filterMethod;
return(false);
}
if (interlaceMethod < 0 || 1 < interlaceMethod)
{
errorMessage = "strange interlace method " + interlaceMethod;
return(false);
}
return(true);
}
private bool AnalyzeChunk()
{
bool result = true;
int length = 0;
byte[] typeArray = new byte[4];
byte[] temp4Byte = new byte[4];
uint crc = 0;
// length area
Array.Copy(pngData, index, temp4Byte, 0, 4);
length = PNGUtil.GetInt(temp4Byte);
index += 4;
// type area
Array.Copy(pngData, index, typeArray, 0, 4);
index += 4;
// data area
byte[] dataArray = new byte[length];
Array.Copy(pngData, index, dataArray, 0, length);
index += length;
// CRC area
Array.Copy(pngData, index, temp4Byte, 0, 4);
index += 4;
crc = (uint)PNGUtil.GetInt(temp4Byte);
// CRC check
if (CRCChecker.CRC(typeArray, dataArray) == crc)
{
result = ApplyChunk(typeArray, dataArray);
}
else
{
// CRC invalid
errorMessage = "CRC invalid";
result = false;
}
return(result);
}