I’ve been playing around with blender and darktable recently. I was trying to use a highpass filter as a mask for soften in darktable but not have it affect the final image, which (except if I don’t understand something correctly) is impossible. Immediately the node editor of blender sprang to mind.

This would allow the result of any filter (especially low and high pass) to be used as a mask (or factor as blender has it) of another filter. Another bonus is that it allows reordering of the filters, and that two completely different pipelines could be mixed right at the end.

Blender has also solved the ease of use problem. It shows the shaders as a list where simple linear structures can be achieved (in Darktable this would mean the existing automatic pipeline priorities) and if somebody needs more fine-grained control he can open the node editor.

This is a mockup of how an actual image processing would work. This pipeline tries to soften the image except in areas like hair, where we do not want to lose detail information.