Re: [Gimp-developer] Adding LAB support to GIMP

[Alexandre Prokoudine <alexandre prokoudine gmail com>]

On Thu, Nov 30, 2017 at 2:44 PM Elle Stone wrote:

> It seems to me that full LAB support would require:
>
> * The option to open images that are in the LAB color space, keeping in
> mind that there are various LAB color space ICC profiles floating
> around, and some LAB images don't have any embedded ICC profile, but
> instead just have metadata that indicates the color space.
>      Upon opening a LAB image, it could be immediately converted to RGB
> for processing, as the conversions from RGB to LAB or LCH for further
> processing in these color spaces are already handled by babl.

So you are not in the scene referred / display referred camp now? :)


> * The ability to do Curves and Levels operations on the LAB channels and
> perhaps on the CH channels.


We briefly discussed this on #gimp a while ago, it's seems to be doable
presently already (but is likely to be somewhat slow).

* Adding L/A/B/C/H histograms to the Histograms dialog: We already have
> Luminance in the histograms dialog. Lightness is just the perceptually
> uniform transform of Luminance.

https://gui.gimp.org/index.php?title=Work_in_progress_on_histogram_redesign

Admittedly, I got sidetracked from this.


> What else might be required to add full support for the LAB space to GIMP?

There's probably a place for LAB/LCH-specific tools, like some iops in
darktable (e.g. color contrast, CLUT, and especially color zones).

Personally, I'm also a big fan of conditional blending (as available in
both darktable and e.g. Photoshop). In darktable, it operates on LAB
channels:

http://www.darktable.org/2012/03/upcoming-features-conditional-blending/
http://www.darktable.org/2012/07/some-enhancements-to-conditional-blending/

In Photoshop, it appears to work on whatever channels as per current color
mode:

https://digital-photography-school.com/photoshop-tips-blend-if-feature/

Alex