private void cvtcmap()
{
for (int i = (1 << bitspersample) - 1; i >= 0; i--)
{
redcmap[i] = (ushort)(redcmap[i] >> 8);
greencmap[i] = (ushort)(greencmap[i] >> 8);
bluecmap[i] = (ushort)(bluecmap[i] >> 8);
}
}