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How do I shape an image?

Jul 15, 2013, 20:45 (This post was last modified: Jul 15, 2013 20:47 by Tarvus.)
Post: #1
How do I shape an image?
Hello everyone. I'm very much a novice Gimp user, but I am trying to learn how to change the shape of an image to fit a specific shape.

What I'm trying to do is reshape a geometrically patterned rectangular image so that the printed image fits around a truncated cone. I'm trying to use the image to create a stencil for glazing a straight sided pottery cup. I know the circumference of the rim and the circumference of the base of the truncated cone so I need to wind up with the borders of the image having a convex curve at the top with the arc length equal to the rim's circumference, a concave curve at the bottom with the arc length equal to the circumference of the base, and with the end points of both arcs connected with diagonal lines equal to the length of the sides of the cup. In addition, I'd like to preserve the image in it's entirety, but distort it as necessary to fit the borders without cutting any of it out. (I attached a sketch in case my pattern shape description was confusing)

Not sure if such a thing is possible with Gimp, but after hours of fruitless Googling, I am hoping somebody here can help me out. Thanks for any pointers you can offer!


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Jul 16, 2013, 00:05
Post: #2
RE: How do I shape an image?
(Jul 15, 2013 22:04)ofnuts Wrote:  However, for a completely different purpose, someone made a script based on the polar coordinates plugin to do what you want:

I played with it a bit and it works as advertised:

- The height of the picture is kept
- The length of the median line is kept (top is stretched, bottom is compressed)
- It works by generating a big image to submit to the PC plugin. The smaller the angle between the two sides, the bigger the image, so it has a built-in lower stop at 45 degrees, but you can edit the file make that lower if you have the memory and CPU Smile

To use the script above, download it, move/copy it to the scripts subdirectory of your Gimp profile and start Gimp again. It will show up as "Filters/theilr/Pan to bow ".

Oh wow! That looks EXACTLY like what I needed ofnuts! Thank you thank you! Smile
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Jul 16, 2013, 14:56
Post: #3
RE: How do I shape an image?
Thanks ofnuts! It took me a while to figure out where my user profile was located and which sub-folder to download the file to, but I finally got it to work! (see attached)

One problem though: I need to use an angle smaller than 45 degrees. (6 degrees, actually). How would I go about editing the .scm file? I viewed it on the download page and think I know WHAT to edit, but what program do I use as an editor? Can I edit the file using Gimp itself? And if so, how?
Thanks in advance for any help you can offer!


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Jul 16, 2013, 16:29
Post: #4
RE: How do I shape an image?
Please disregard my last question, ofnuts. I downloaded notepad++ and edited the script file with that. Worked like a charm, but the memory issue did arise when I ran the script. I worked around it by resizing the image by 1/3rd, running the script to modify the shape, and then resizing the results back up to my required size.

Here's a pic of the mug with pattern for the stencil attached. Thanks again for your help! This particular script is going to get a lot of use in my pottery decorating!


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