Sorry for the confusion. I wasn’t trying to say that the point of step 3 was to simulate the characteristics of the scanner (à la VSCOs Noritsu/Frontier attempts), but rather to assume a perfect digitization with some ability to tweak black and white points and a curve so (that the exported file can be sent for print).
Perhaps this becomes more philosophical than technical, but what we do when we export the picture (or “Save Selected Layers”) from agx-emulsion is the equivalent of scanning the print. My thought was that it could make sense to give the user basic control over this “scan”.
Thanks for reiterating. I realize now how fantastic this sounds and perhaps it would be enough for your app. I’ll download and give it a try. There’s always GIMP to do further “post scan” corrections. 
When agx-emulsion gets implemented in other apps (like vkdt or darktable), levels and curves can be applied via modules placed post agx-emulsion if necessary.
Speaking of darktable. How difficult would it be to port GLSL code C for module use in darktable? Perhaps a question for @hanatos, @flannelhead or @Pascal_Obry?
Dang, no results!
