Rich Evans wrote: > Ken --- close. but no cigar... > the steps: 1) Colors -> Desaturate; 2) Colors -> Invert leaves me with a > greyscale image... all color is gone :-( I'm looking for a filter that will > invert only black, white and grey pixels... leaving color saturated pixels > alone. > > Owen --- I will investigate the python solution. thanks for the advice. > > All --- Maybe the best question to ask is this... where online should I go to > learn about how GIMP filters are developed? I suppose once I learn how to > make on filter.. I suspect I will quickly conjure up other filter ideas as > well... > Meanwhile (and bearing in mind you haven't let us see the image in question), would this work?: Duplicate layer, invert bottom layer and cut all blacks and whites out of (transparent) top layer (of course, if there's a range of greys it gets more complicated). Andrew > For completeness, my original question is this: I have an RGB image that is > basically a black background with many > colorful objects and white text. --- I'd like to invert the image so > that it is a white background with black text but a simple invert > inverts the colors in all the colored objects as well. Is there a > technique or tool to invert any part of the image that is only a shade of > grey? > i.e. invert pixeils with a saturation of ~0 (if that is how you say > it). I could imagine a filter that does a simple RGB invert for any > pixel whose calculated RGB saturation value is below a set threshold. > Does this type of tool/script exist? > > > continued thanks, > -rich > > > ----- Original Message ---- > From: Ken Warner <kwarner...@verizon.net> > To: Rich Evans <reva...@yahoo.com> > Cc: Gimp-user@lists.XCF.Berkeley.EDU > Sent: Tue, February 2, 2010 8:12:09 PM > Subject: Re: [Gimp-user] how to invert greyscale values only... > > Colors -> Desaturate; Colors -> Invert > > No? > > Rich Evans wrote: > >> I'm grateful for the replies I have received, but I was thinking that if >> there isn't a well-known tool or method already, that maybe someone could >> point me to a site that describes how custom filters can be made from >> scratch. I'm not afraid to learn what I need to to make the filter, ...I've >> just never done it before. *grin* I just need someone to point me to a >> decent tutorial (I can do c programming if that's what it is, but my working >> assumption is that, all things being equal, it should be easier to make a >> filter for GIMP than it would be to write a c program from scratch).Would >> anyone consider this... easy? >> >> continue thanks, >> -Rich >> >> >> >> ----- Original Message ---- >> From: Cédric Gémy <radar.ma...@free.fr> >> To: Gimp-user@lists.XCF.Berkeley.EDU >> Sent: Tue, February 2, 2010 5:58:51 PM >> Subject: Re: [Gimp-user] how to invert greyscale values only... >> >> not completely satisfied with sven's method, working on some pictures >> but not any, depending on the shades. >> I used to do it in CMYK a long time ago with photoshop by just pushing >> the image to CMYK and inverting the K curve. >> I guess something might be done with decompose color filter or so. But >> the quicker/best average i've found is just adding a mask based on the >> layer (L from Lab or N form CMYK could be used too), and play with the >> curve to adapt to the shades+refine with brush on mask. It takes few >> seconds if the picture is not too complex. Then put a white layer below >> and it's quite done. But i'm not completely satisfied with it. >> >> _______________________________________________ >> Gimp-user mailing list >> Gimp-user@lists.XCF.Berkeley.EDU >> https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user >> >> >> >> _______________________________________________ >> Gimp-user mailing list >> Gimp-user@lists.XCF.Berkeley.EDU >> https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user >> >> > > > > > _______________________________________________ > Gimp-user mailing list > Gimp-user@lists.XCF.Berkeley.EDU > https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user > >
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