I have a photograph of a tree bark texture, and I'd like to flatten it out to use as a generic bark texture. It's fairly "flat" now but there's a noticeable curve to the edges of the texture. I'd like to "straighten out" those edges so I can more easily make the image tillable.

I hope that makes sense. I'm using GIMP.

Here's the texture. You can see at the edges it does start to noticeably curve a bit. As long as the result looks OK, almost any technique will do.

tree bark texture

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    I can't tell if you want to actually flatten the cylindrical shape of the tree, which in my opinion isn't really even distinguishable in the image, or if you want to straighten the texture? I think you want to straighten the texture, but I could be wrong. By straightening the texture I mean something like this, in which I did not flatten the cylindrical shape of the tree, but just made the texture straighter. If you feel that image visualizes what you want to do, you can copy the link and add it to the question. – Joonas Oct 3 '18 at 8:03
  • I suggest you ti read this: dsp.stackexchange.com/questions/2406/… – Paolo Gibellini Oct 3 '18 at 8:46
  • Oh hey actual replies. Thanks @Joonas but I'm not sure what you mean either. :-) tThere's a slight but obvious curve to the texture at the left and right edge. If I tiled the image I'm sure it would be really obvious to a viewer. So I want to "bend" the edges so that there's less obvious perspective to the size of the tree bark texture. P.S. Took a look at your link and that's not what I meant. I may have to do that as well, but that wasn't what I intended. So I guess not "straighten" but I want to reduce the cylindrical shape of the tree and texture. – markspace Oct 3 '18 at 16:43
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    Thanks @PaoloGibellini I don't speak Mathematica but that's a good article on the basic technique. If I could do that in GIMP it would be easiest for me. – markspace Oct 3 '18 at 16:51

Create a white to black gradient, and use that in Filter>Map>Displace for the X coordinate to stretch out the edges (move them further way as a function of their distance to the center). You can use Curves to change the gradient (S-shaped curved) to better match the actual curve you would need:

enter image description here

  • This seems like the most workable solution. Thanks for posting. It figures that GIMP's solution would be "first make a gradient on another layer..." :-) – markspace Oct 3 '18 at 16:53
  • This does seem to be what I was asking for. If I have additional questions I'll just make another question. Thanks again to everyone! – markspace Oct 3 '18 at 19:57

I would use Tools > Transform Tools > Warp Transform. The tool is also located in the toolbox.

If you set the size of the tool large but keep the strength low, it's a very easy fix.

enter image description here

  • This is also a nice solution, though I'm not sure I trust my hand is steady enough to do this accurately. Good for those with more confidence in their drawing skills. – markspace Oct 3 '18 at 16:54
  • @markspace If you keep the strength of the warp tool low, you can just do it in short multiple steps, then it's not so difficult. – Billy Kerr Oct 3 '18 at 17:11

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