Luke Campagnola schrieb: > It's been a while since I originally brought this up, but I've pulled out > the ol' scanner for another go. > to recap: color calibration isn't quite right on my canon lide35--the dark > colors drop out to black. I turned on SCAN_FLAG_DISABLE_SHADING as you > instructed, and as you predicted this recovered my lost dark colors. Where > should I go from here? Should I crank up SANE_DEBUG_GENESYS and send you > the > scanimage output and *.pnm files? > > Thanks, Luke >
Hi Luke, Did you try with sane from cvs? There have been some bug fixes. If that does not show the dark colors, use SANE_DEBUG_GENESYS=255 and SANE_DEBUG_GENESYS_GL841=255 with scanimage in color mode, and send the resulting error output and the generated .pnms. Regards, Pierre > > On 3/7/06, Pierre Willenbrock <[email protected]> wrote: >> >> > - Color reproduction is better with the sane driver than the windows >> driver, >> > which tends to boost the reds way too much (yaay) >> > - Brightness reproduction is quite poor with the sane driver. It seems >> that >> > darker colors just drop off to black very quickly. >> >> A better tool to determine if the bright and dark colors are correctly >> reproduced is a histogram tool. You can clearly see, if there is still >> room at the bottom and top of the histogram(not too much, as you still >> want some useable color values ;-)). >> >> This reveals that dark colors are cut off for the sane driver, but it >> also shows that the windows driver cuts off bright colors. >> >> Anyway, it shows a incorrect calibration on the sane side. > > <snip> > >> To get an unshaded image, you can disable shading correction in >> gl841_init_regs_for_scan by changing the flags(last parameter to >> gl841_init_scan_regs, currently 0) to include SCAN_FLAG_DISABLE_SHADING. >> >> If the image then still shows dark colors cut off, the offset/exposure >> calibration is to blame. Otherwise the shading calibration calculates >> incorrect data(which i suspect). >> >> I should put this lengthy description online somewhere.. >> >> Regards, >> Pierre >> >
