Replace "Auto" in the Blend space and Composite space dialogs with something more informative
@ellestone
Submitted by Elle Stone Link to original bug (#783743)
Description
Please replace "Auto" in the Blend space and Composite space dialogs with something more informative, such as "Auto (Linear)" when "Auto" means RGB encoded linearly, and "Auto (sRGB TRC)" when "Auto" means RGB encoded using the sRGB TRC.
The problem: Some "Default" blend modes use linear RGB, and some do not.
Currently the only way to be 100% certain that a layer is blended using linear RGB is to right-click on the layer in the layer stack, choose the Blend and Composite spaces, and set them both to linear. Otherwise, the Blend and Composite spaces are "automatically" set to "Auto", which doesn't inform the user as to what "Auto" means for the particular blend mode in question.
For an example of why "Auto" is insufficiently informative, my editing goal was to introduce haze into an image by doing the opposite of removing haze using "high radius low amount" USM. Grain-extract was one of the steps, and for "reverse haze removal", grain-extract required being done using linear RGB.
It took a while before I figured out why my "reverse haze removal" procedure was failing at the grain-extract step. But after consulting the source code, I realized that for GIMP's Default blend modes, grain-extract uses Perceptual Blend/Composite spaces. Changing to Linear fixed the problem.
Users really shouldn't have to consult the source code to know whether a blend or composite space is using linear RGB or RGB encoded using the sRGB TRC.
It would be very helpful if "Auto" in the UI were supplemented with information as to whether in any given case "Auto" means RGB encoded using the sRGB TRC or whether it means linear RGB.
Version: git master