[softwarelist] Re: Calibrating scanner with TWAIN
- From: Michael Ben-Gershon <mybg@xxxxxxxxxxxxxxxx>
- To: davidpilling@xxxxxxxxxxxxx
- Date: Thu, 10 Aug 2006 16:17:55 +0300
David Pilling wrote:
In message <44DA5FC0.2060701@xxxxxxxxxxxxxxxx>, Michael Ben-Gershon
<mybg@xxxxxxxxxxxxxxxx> writes
Where do I start? I know the screen and printer are calibarted
together, but how do I adjust the scanner?
<sigh> At last someone who would like ICC colour profile support on
RISC OS.
One comment is that the Epson driver lets you pick from a menu a
number of Epson colour corrections - these date back to the earliest
Epson scanners. I'm not sure how useful they are, but perhaps picking
the wrong one might give poor results.
Knowing what I know now (i.e. in the light of profile support in
DPScan and Ovation Pro on Windows) it would be easy to make the TWAIN
driver take in an ICC profile and put out standard sRGB.
It is unlikely I will do any more work though.
Later Epson scanners allow a colour matrix to be uploaded into the
scanner. Perhaps that allows the scanner to do the correction in the
ICC profile and at higher resolution than the 8 bits the driver sees.
I suppose there may be the possibility that the colour matrix is left
in a non-standard state. For some scanners I've heard it said that
scanning from Windows and then RISC OS gives different results to just
scanning from RISC OS from cold.
My TWAIN driver will let you do some colour correction - you can
twiddle the RGB gamma curves independently of the overall brightness.
There's also a detint button to help you set things (scan something
white and then click the button). However this is not going to be fun.
Well, I started with the detint button, which (surprisingly) did not
give consistent results. However, it was a start. I then played about
with the individual RGB settings (brightness and contrast) until I
could get a feel for what they were each doing. The, armed with a
quite accurate colour chart I finally managed to get what I reckon
is a pretty good colour scan. Of course, I have now saved the results!
Michael Ben-Gershon
mybg@xxxxxxxxxxxxxxxx
Other related posts:
