On Tue, Jun 19, 2012 at 3:24 PM, Elle Stone <l.elle.stone@xxxxxxxxx> wrote: > (1) Color space conversions result in lost colors, whether done at 8-, > 16-, or 32-bits, floating or integer. At first I thought it was a > result of converting to and from a linear-gamma color space. But > actually the color space gamma makes no difference. > (2) All the color space conversions that I used involved matrix > profiles. For a matrix profile, the only valid type of color space > conversion is "colorimetric". I used "relative colorimetric" color > space conversion exclusively. The color space conversion results > varied depending on whether I used black point compensation or not. > However, if the color spaces involved all have the same black point, > using or not using black point compensation should not make any > difference whatsoever. None of the ICC profile handling in GIMP deals with GEGL or higher bitdepths - at the start and end of all these code paths things go through 8bpc; and probably behave similarly to how they do in 2.8 - there shouldn't be much of a difference. > (3) Eric Brasseur's image scaling test produced very odd image > discolorations, regardless of what color space (linear or nonlinear > gamma) or image depth (8-bit integer or 32-bit floating) was used. I've seen some of these discolorations; but at least the results are a lot more correct than earlier versions, for some of these tests the type of resampler and "where in the pixel" the center being resampled is will matter a lot, the 2x2 px in input -> 1 px in output hardcoded tests used by eric brasseur are not generic like the code paths employed by gimp. > (4) Although Gimp 2.9 correctly opens 8-bit tiffs, when opening any > 16-bit tiff, the image is subjected to a roughly gamma=2.2 curve. All > RGB colors are altered (it's not just a display problem), so the > resulting image is too light. TIFFs seem to be a nightmare and only brief initial attempts have been made at making GIMP support higher bitdepth diffs. /Øyvind K. -- «The future is already here. It's just not very evenly distributed» -- William Gibson http://pippin.gimp.org/ ; http://ffii.org/ _______________________________________________ gimp-developer-list mailing list gimp-developer-list@xxxxxxxxx https://mail.gnome.org/mailman/listinfo/gimp-developer-list
