public void getSOF(SOFInfo sof, UInt32 offset, UInt32 size)
{
if (!input.isValid(offset, size))
{
throw new Exception("getSOF: Start offset plus size is longer than file. Truncated file.");
}
try
{
Endianness host_endian = Common.getHostEndianness();
// JPEG is big endian
if (host_endian == Endianness.big)
{
input = new TIFFBinaryReader(input.BaseStream, offset, size);
}
else
{
input = new TIFFBinaryReaderRE(input.BaseStream, offset, size);
}
if (getNextMarker(false) != JpegMarker.M_SOI)
{
throw new Exception("getSOF: Image did not start with SOI. Probably not an LJPEG");
}
while (true)
{
JpegMarker m = getNextMarker(true);
if (JpegMarker.M_SOF3 == m)
{
parseSOF(sof);
return;
}
if (JpegMarker.M_EOI == m)
{
throw new Exception("LJpegDecompressor: Could not locate Start of Frame.");
}
}
}
catch (IOException)
{
throw new Exception("LJpegDecompressor: IO exception, read outside file. Corrupt File.");
}
}
public void parseSOF(SOFInfo sof)
{
UInt32 headerLength = (uint)input.ReadInt16();
sof.prec = input.ReadByte();
sof.h = (uint)input.ReadInt16();
sof.w = (uint)input.ReadInt16();
sof.cps = input.ReadByte();
if (sof.prec > 16)
{
throw new Exception("LJpegDecompressor: More than 16 bits per channel is not supported.");
}
if (sof.cps > 4 || sof.cps < 1)
{
throw new Exception("LJpegDecompressor: Only from 1 to 4 components are supported.");
}
if (headerLength != 8 + sof.cps * 3)
{
throw new Exception("LJpegDecompressor: Header size mismatch.");
}
for (UInt32 i = 0; i < sof.cps; i++)
{
sof.compInfo[i].componentId = input.ReadByte();
UInt32 subs = input.ReadByte();
frame.compInfo[i].superV = subs & 0xf;
frame.compInfo[i].superH = subs >> 4;
UInt32 Tq = input.ReadByte();
if (Tq != 0)
{
throw new Exception("LJpegDecompressor: Quantized components not supported.");
}
}
sof.initialized = true;
}
