> I have an image of a painter's palette. I have both the original
> color version and my grayscale reproduction. What I really want is a
> line drawing of the outline. Can anyone suggest a sequence of steps to
> arrive at this? 

Hi John -

This counts as a Hard Problem (TM), for which there is no general solution.  I 
can suggest a variety of tricks and tactics that I have used with varying 
degrees of success - ymmv.

First, for some good background on this problem, try reading Chapters 3 and 4 
(Selections, and Channel Masks) of Grokking the Gimp, by Cary Bunks.  The book 
itself is available online at gimp-savvy.com, or you may download it.

1. The most general, and the most tedious, way to outline an object in an 
image is to use the bezier selection tool.  Personally I have never liked this 
tool, as it's way too finicky, and I keep making selection mistakes such as 
editing the path when I want to simply move a point, etc.  But, if you can 
take the time, it will outline things to any degree of detail you have the 
patience for.

2.  Other selection tools can work nicely if there is some way to discriminate 
between the object you're trying to select and its immediate background.  Try 
decomposing the original image to HSV channels, for example, and selecting 
using the magic wand in the Value or Hue channels, for example.

3.  Or try using <Image>/Colors/Threshold.  Sometimes this will distinguish 
nicely between useful parts of an image.

4.  And, of course, there are the various edge-detection filters:  including 
Laplacian, LoG, Sobel, etc.

Conclusion - some features of an image are more easily extracted than others.  
If you're lucky, the item you want to cut differs noticeably in color from its 
solid background, and it's easy (more or less).  If you're working with a 
normal photo, then no simple feature set distinguishes the target objedt from 
the background and you have to work a lot harder.

Good luck, and good hunting!


Jeff Trefftzs <[EMAIL PROTECTED]>
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