Better UI: Show HUE in the graph for hue equalizer

[tobiasBora]

Darktable has a really cool GUI to see HUE eqalizer like:

In comparison the HUE equalizer in ART (via CTL scripts) is not that nice:

In particular, it is fairly hard to know what is the new HUE since nothing is printed in the y axis. Similar modifications for other curves (saturation, luminosity etc) would also be great.

As a second request, it would also be really cool if the HUE of the pixel under the mouse would be visible in the graph in order to let me know where to change the graph.

[agriggio]

Hi,
Both features are available in the built-in (global) colour equaliser. There's currently just not enough wiring to do this in a CTL script. Adding such level of integration for scripts that can implement arbitrary pixel level operations would be non trivial I'm afraid

[tobiasBora]

Thanks for the answer.

There's currently just not enough wiring to do this in a CTL script.

What do you mean? It seems like the description of the input in CTL scripts is an art-specific type like @ART-param: ["hcurve", …. So why can't ART define a special kind of control like hcurve_hue, hcurve_sat etc to create this kind of more advanced control, with better GUI + implementation wf the mouse cursor?

[agriggio]

Because there's no such thing as "the hue". There are many definitions of hue, depending on the colour space used, and art doesn't know what the ctl script will use.
On any case, I didn't say impossible, just non trivial. I'll be very glad to get a patch/pull request that allows this while still being general enough to support arbitrary pixel-level operations using arbitrary representations of colour.