Bug 151171

Summary: Need support for adjusting in HSV and HSL colorspaces
Product: [Applications] digikam Reporter: Dik Takken <kde>
Component: Plugin-Editor-CurvesAssignee: Digikam Developers <digikam-bugs-null>
Status: RESOLVED FIXED    
Severity: wishlist CC: caulier.gilles
Priority: NOR    
Version First Reported In: 0.9.2   
Target Milestone: ---   
Platform: Gentoo Packages   
OS: Linux   
Latest Commit: Version Fixed/Implemented In: 8.0.0
Sentry Crash Report:

Description Dik Takken 2007-10-22 11:18:38 UTC 
Version:           0.9.2 (using KDE KDE 3.5.7)
Installed from:    Gentoo Packages
OS:                Linux

The Adjust Curves plugin would be immensely more powerful when you can apply the curve on individual channels in the HSV and HSL color spaces. So, apart from R, G and B, there should be four additional channels: H, S, V and L. 

Having both L and V is a key feature here, because HSL reduces saturation as you darken the image, while HSV increases saturation as you darken the image. In case you have a bright washed-out sky that needs adjusting, you adjust the V channel in HSV space. In case you have a dark lifeless foreground, you adjust the L channel in HSL space.

Having both a color space dropdown menu and a channel dropdown menu would be even better.

http://www.normankoren.com/light_color.html
Comment 1 caulier.gilles 2023-04-06 14:57:51 UTC 
Image Editor G'MiC-Qt tool with Colors/Curves filter also to adjust HSV or HSL color spaces.

https://i.imgur.com/eqB61BV.png

Gilles Caulier