2018-03-07 16:13 GMT+01:00 Romano Giannetti <romanof...@rgtti.com>: > > On 07/03/18 11:32, Matthieu Moy wrote: > >> Before considering a fix: any idea how the "substract" operator should >> >>> act in the Lab color space? >>> >> I have no idea ;-). >> >> Actually, my guess is that "subtract" is useful to blend two totally >> different images together (e.g. blend a black&white text onto an image >> for a dodge&burn effect). For darktable where blending is done between >> the original image and the image transformed by the module, I'm not >> even sure "subtract" is a relevant thing to do. The fact that it's been >> broken for years without anyone noticing is probably a sign that no >> one ever found it useful. >> >> > I am guilty of never using it in darktable, but the usage could be to see > _where_ in the image the applied module is acting. I mean, for example, if > you really are subtracting, and you are applying an high pass, you should > see a black image (no variation) with just the edge highlighted. >
[OT] I usually do this with difference blend mode. For example when I want to know in which areas affects equalizer I change temporary to difference blend mode and can see it. > > Romano > > -- > Romano Giannetti > http://www.rgtti.com/ > > > ____________________________________________________________ > ________________ > darktable user mailing list > to unsubscribe send a mail to darktable-user+unsubscribe@lis > ts.darktable.org > > -- Enviado desde mi tabla de planchar ____________________________________________________________________________ darktable user mailing list to unsubscribe send a mail to darktable-user+unsubscr...@lists.darktable.org
