Hello, To preserve luminosity when using the Channel Mixer module one must be careful in choosing values for the red, green and blue sliders such that their sum equals 1. If we need to change the sliders values a lot (e.g. when experimenting with their importance on a black and white conversion), it becomes very slow and painfull to drag all others sliders appropriately to keep the overall luminosity. Mainly when you use differents values for different parts of a single image. It would be much faster and easier to have an option to keep the image luminosity, like in Gimp's channel mixer ( https://docs.gimp.org/en/plug-in-colors-channel-mixer.html). This is relatively easy to implement: we just need to divide the computed value by the sum of the three chosen weights. I took a look at this module's source code and identified the pieces that must be changed (including the opencl kernel). If you agree this feature is a good idea, I may help implementing it. What do you think?
Cheers -- Caio S. Souza Laboratório de Biologia Teórica e Computacional Universidade de Brasília www.lbtc.unb.br ___________________________________________________________________________ darktable developer mailing list to unsubscribe send a mail to darktable-dev+unsubscr...@lists.darktable.org
