gwidion@xxxxxxxxxx (2003-07-24 at 2031.28 -0300): > The basic idea is that besides the "normal" "addition" " darken only" > layer modes, to implement a "custom mode". In it, the user gets to > type a c-like expression of what to do with the pixel values > in each channel when combining the layer. IMO you are forgeting a kind that users will like a lot more: call other GIMP functions, specially some like levels or curves (in this case, using the layer to control strengh in a channel by channel basis, or maybe using value (V in HSV) to get a single number and work like a selection mask, you should have to checke what makes sense). I guess users will find more use to those than playing around with formulas. I used the filter that lets you do math formulas to test ideas, but dunno how many people would like to use that daily. The formulas are nice, I am not saying you should drop that, but you should find a way to cover both if you can, formula and PDB. If you are going to get dirty, make it really worth it. Maybe even you can do the PDB way only, and provide a new call that does formulas (sounds simpler to me, more generic). Hey, maybe you can fit into it effect layers. ;] Well, probably not, they are not simple operations to layers below them. Depends if you want to apply filter to the result, which is just the call idea, or to the layer data only, which is what you need for auto bevel or auto drop shadow when working with text, ie. Last case would be more like having a layer hidden as input and a visible one as output, and recalculate output one only when input changes, not every time layers below change. In any way, all are interesting ideas to explore. GSR