Daniel Hornung wrote: > On Wednesday 24 September 2008, Chris Moller wrote: > >> Maciej Pilichowski wrote: >> >>> So there is obstacle, indeed. And till now I have no idea how to solve >>> this. >>> >> Might be a bit of a wild branch on this topic, but I'm wondering if all >> the effects described here could be implemented as a /subtractive/ process. >> >> I haven't looked at gimp's implementation, but generally speaking colors >> combine as Cr = Ce * ( 1- o) + Cb * o, where Cr is the resultant color >> (clamped full saturation of each of it's components), Ce is the existing >> color, Cb is the brush color, and a is the opacity. What if, instead, >> you made Cr = Ce * (1 - o) - Cb * o, with Cr clamped at 0? All this >> doesn't fiddle with the alpha channel at all, but might get the desired >> effect. >> > > Isn't that pretty much what the 'subtract' mode does? And yes, it doesn't > involve the alpha channel. > http://docs.gimp.org/en/gimp-concepts-layer-modes.html > > Yeah, I expect it's the same function, but adding a transparent layer, painting it, switching to subtract mode, and merging down, is more cumbersome than just painting in subtract mode would be. cm > Daniel > > ------------------------------------------------------------------------ > > _______________________________________________ > Gimp-developer mailing list > Gimp-developer@xxxxxxxxxxxxxxxxxxxxxx > https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer > -- Moller Software Development Services *Christian H. L. Moller* /President/ *Moller Software Development Services, LLC* ** moller@xxxxxxxxxxxxxx 919.367.8689 (Voice) www.mollerware.com <http://www.mollerware.com> 919.367.9097 (Fax) ** ** _______________________________________________ Gimp-developer mailing list Gimp-developer@xxxxxxxxxxxxxxxxxxxxxx https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
