Some devices can compress colour (JPEG) and also provide raw data
in uncompressed form. The two devices that I have supply raw data
not in RBG but in YCbCr form.
Now applications have the option to choose compressed or uncompressed
colour scans if supported by the device.
Cancel from the device by pressing STOP is now handled properly.
Test machine MFC-290C seems to support JPEG and RAW colour data.
However, the raw colour data has what appears to be a strong green
component leading to very green images. Maybe some post processing
is required to generate a proper image. Dunno. JPEG looks perfectly fine.
Still one rare illusive issue that causes loss of a bit of a line's
data, resulting in a sliding of the image to the left. It doesn't
happen very often, very difficult to reproduce.