[sane-devel] HP5470c scanner nearly working!

[David Stevenson]

On Wednesday 19 February 2003 10:52 pm, Martijn van Oosterhout wrote:
> This is only a test program, not a backend. Things still to do:
> 1. Actually use results of calibration scans. Anyone who has an idea how
> scanners are calibrated, point me at some info, please.
Martin
I did some work on gains and offsets for the GT68xx backend, the CCD version. 
The CIS version is somewhat different.
I was mostly porting the code supplied by the manufacture but the principal 
was fairly straight forward.
Loop 6 times,  adjusting by trial and error, scanning the line with it's 
black mark and white strip to set the offset. With a low gain, read an 
average white and and average black and adjust offset till these are equal 
distance from mid point. 
Then start looping to set the gain.
This was done for each colour building the gain till the avg signal level was 
near max.

Let me know if you need any more details.
David