Re: [Gimp-developer] Histograms in unbounded mode sRGB


Am 18.04.2014 22:10, schrieb Elle Stone:
I think the only reasonable solution is to keep the WideGamutRGB 
chromaticities available for use as an editing/compositing color space, 
and use that color space to display histogram information (and also to 
display Color Picker and Color Selector information).

please allow me to make the case for using the color space of the respective
export file format for histogram displays.

You recently gave striking examples of how working with RGB _numbers_ can quickly
become unwieldy from a user point of view. This probably applies as soon as the
limitations of the traditional 8-bit sRGB processing are relaxed. There is
nothing wrong with RGB color models, it is just that the numbers can become
difficult to interpret for human beings.

So, as a thought experiment, i'd like to get rid of any kind of RGB triples in the
UI. To see where it hurts the most. This will be the places where RGB numbers are
really needed. After all, GIMP is about colors, not numbers.

Say, we get an adobeRGB camera image and the task is some touch-up and warping.
The deliverables are 1) a JPG for the web and 2) a proPhotoRGB file for that mega
stock company.

I find that most of the editing can be performed without looking at a single RGB
triple. Image transforms do not expose RGB numbers, neither do most of the filters.
Even many of the tools in the Colors menu do not refer to RGB numbers. Of course,
this is different for levels/curves. But by large, these tools are used on the 'value'
channel, not on the distinct R,G,B channels. Here, working on the luminance channel
instead would probably be an improvement.

I find it is only on *export* when the RGB numbers become really important. Much like
output-specific scaling and sharpening, each of the deliverables needs specific
color treatment.

Here, the histograms need to show the R,G,B channels of the specific output color
space to allow assessment and correction of the conversion. Probably, this is also
where the curves/levels tools should be working in the output color space. For
example, how else could someone boost the midtones without adding clipping -- when
maximum and minimum range of the curve do not refer to the actual range of the
output file format? (not even talking of non-matching color primaries here)

These color modifications that are specific to the output files are hot candidates for
being stored in export pipelines, again analogous to scaling and sharpening operations.

I'm less sure in how far this is an analogy to CMYK export -- is an equivalent to
the 'press projection' needed here? Or is it sufficient to set the RGB color space
of histogram/curves etc. to the currently active softproofing color space?

best regards,

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