On Wed, Mar 11, 2009 at 10:33 AM, Rob Antonishen<rob.antonishen@xxxxxxxxx> wrote: > Sven mentioned other uses, like spot colour and halftoning. I can't> find any references on using gimp channels for spot colour, in fact> google only finds me claims that a weakness of gimp is that it does> NOT support spot colours. GIMP does offer spot channels, but there is no (easy) way to outputthe spot channels directly to a printer in grayscale. Nor does thechannel mixer operate on the spot channels. I use spot channels to create separations for printing. Each spotchannel corresponds to a positive that will be used to create a screen(plus one channel to represent the substrate). In PS, one can turnoff the RGB channel and use the visibility of the spot channels tosimulate the final output on the printing press. Turning offeverything except one spot channel renders that spot channel ingrayscale (which makes printing the single channel very easy).Turning on two or more spot channels renders them in RGB. This isincredibly useful when setting up multicolor prints (think of a whiteunderbase for printing a bright color on a dark substrate). I can work around most of these things in GIMP by doing things likereloading the channel as a selection, creating a new layer and fillingit with black and printing just that layer - but it can be quitecumbersome. Also, PS supplies a very badly-named function called"Apply Image" that allows you to take the contents of any givenchannel and apply it to the contents of any other channel using theavailable blending modes (multiply, screen, etc.). This is the realpower behind channels. 99% of people will likely not need spot channels, but to the reaming1% they are quite useful. Hopefully with the coming of GEGL it willbecome easier to do some of this pre-press separation and channelmixing. Chris_______________________________________________Gimp-developer mailing listGimp-developer@xxxxxxxxxxxxxxxxxxxxxxxxxxx://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
