On 24/09/2010 17:05, Joao S. O. Bueno wrote: > > On Fri, Sep 24, 2010 at 11:19 AM, Ofnuts<ofnuts@xxxxxxxxxxx> wrote: >> Hi, >> >> My code needs to do a one-pixel-wide selection, at distance "x" from the >> current selection. This looks a lot like a border selection except that >> the border selection creates at best a two-pixel wide ribbon and I only >> want one (but if I'm wrong, please tell me how to :-) >> >> So far my code goes like this: >> >> # Selects pixels that are between x and x+1 pixels from >> # the original selection. Bumping the selection by one >> # each time doesn't work, a small circle degenerates into >> # a square with rounded corners instead of a big circle. >> def select_ribbon(self,image,selection,dist): >> pdb.gimp_selection_load(selection) >> pdb.gimp_selection_grow(image,dist+1) >> outer=pdb.gimp_selection_save(image) >> pdb.gimp_selection_load(selection) >> pdb.gimp_selection_grow(image,dist) >> inner=pdb.gimp_selection_save(image) >> pdb.gimp_channel_combine_masks(outer,inner,CHANNEL_OP_SUBTRACT,0,0) >> pdb.gimp_selection_load(outer) >> image.remove_channel(outer) >> image.remove_channel(inner) >> >> That works, but can be slow (especially since it's at the core of a >> loop). Is there any better way? Or useless code to jettison? >> >> Next improvement is to create a 3-pixels selection and feather it one >> pixel. Anything to be wary of? > > Hmm..this _will_ be slow. :-) > > You can speed it up by making a copy of your drawable to another > image, disable the undo system on this new image and perform your > cations above, before copying the results back to the original image - > but it is about it. > Maybe you can perform the whole loop in the copy with undo disabled - > but I don't know your intent. The whole plugin paints successive concentric uniform 1-pixel ribbons around the original selection (pixel values a obtained from another layer). On my laptop (T2400, 1.83GHz) it takes roughly 10 seconds to draw 20 concentric ribbons around a 500-pixels circular selection. The whole thing runs within a undo_group_start()/image.undo_group_end() so I don't expect any more undos? _______________________________________________ Gimp-developer mailing list Gimp-developer@xxxxxxxxxxxxxxxxxxxxxx https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
