public SOFInfo GetSOF(uint offset, uint size)
{
// JPEG is big endian
if (Common.GetHostEndianness() == Endianness.Big)
{
input = new ImageBinaryReader(input.BaseStream, offset);
}
else
{
input = new ImageBinaryReaderBigEndian(input.BaseStream, offset);
}
if (GetNextMarker(false) != JpegMarker.SOI)
{
throw new RawDecoderException("Image did not start with SOI. Probably not an LJPEG");
}
while (true)
{
JpegMarker m = GetNextMarker(true);
if (m == JpegMarker.Sof3)
{
SOFInfo sof = new SOFInfo();
ParseSOF(sof);
return(sof);
}
if (m == JpegMarker.EOI)
{
throw new RawDecoderException("Could not locate Start of Frame.");
}
}
}
public void ParseSOF(SOFInfo sof)
{
uint headerLength = input.ReadUInt16();
sof.precision = input.ReadByte();
sof.height = input.ReadUInt16();
sof.width = input.ReadUInt16();
sof.numComponents = input.ReadByte();
if (sof.precision > 16)
{
throw new RawDecoderException("More than 16 bits per channel is not supported.");
}
if (sof.numComponents > 4 || sof.numComponents < 1)
{
throw new RawDecoderException("Only from 1 to 4 components are supported.");
}
if (headerLength != 8 + sof.numComponents * 3)
{
throw new RawDecoderException("Header size mismatch.");
}
for (int i = 0; i < sof.numComponents; i++)
{
sof.ComponentInfo[i].componentId = input.ReadByte();
uint subs = input.ReadByte();
frame.ComponentInfo[i].superV = subs & 0xf;
frame.ComponentInfo[i].superH = subs >> 4;
uint Tq = input.ReadByte();
if (Tq != 0)
{
throw new RawDecoderException("Quantized components not supported.");
}
}
sof.Initialized = true;
}
