> 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
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]>
http://www.tcsn.net/trefftzs Home Page
http://gug.sunsite.dk/gallery.php?artist=68 Gimp Gallery
http://trefftzs.topcities.com/ Photo Gallery
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