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So, a while back I created this icon from a game, but looking back on it behind a white background instead of an alpha-channel its edges are super choppy in some places while it's smooth in others, which is possibly due to the method I used to select certain regions before bucket-filling it. I was using GIMP and I was wondering if there is any possible way to easily fix this (ie make all edges even instead of choppy). Maybe some rendering filters or selection methods that I don't know about? I've googled and youtubed but with no avail.

My image:

http://fc05.deviantart.net/fs71/f/2013/177/7/c/seal_of_mar_by_jacedc-d695fa3.png

(As you can see, the inner crescent-shaped things are choppy as well as the exterior of the circle on the left and right is choppy)

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    You've tagged is as raster and state you used Gimp. Raster apps are always going to result in some pixels at the edges of arcs. If you use a vector application, you can get cleaner lines.
    – Scott
    Jun 26 '13 at 21:27
  • @Scott Well I was the one that tagged it as raster (though it's clearly a raster image)
    – Ben Brocka
    Jun 26 '13 at 21:33
  • I used GIMP and somewhere along the lines (no pun intended) it ended up looking like a really choppy raster image. I was wondering if there's a quick solution to just round out all of the edges.
    – Jacedc
    Jun 26 '13 at 21:34
  • @BenBrocka - the question states Gimp.. so raster is a good tag. not sure why it was removed. Jacedc - are you asking how in Gimp??? As I've commented, a raster app isn't going to offer many more solutions. There is no "magic' button.
    – Scott
    Jun 26 '13 at 21:45
  • In order to avoid the "choppy" edges for future images you create this way: make sure that all your selections are feathered.
    – Michael Schumacher
    Sep 28 '15 at 7:19
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I'd say there's no quick and dirty fix for choppy lines, you just gotta recreate it using vectors. The following took me 3 minutes in Photoshop with Circles and Stroke effect:

Logo Example

I'm not going to do it all for you, but all you need is two more half circles and you've got a shape based logo, which should scale beautifully to any size. So that's 6 circles, two semi-circles and a stroke applied to some of them. In your case it's very simple to recreate, but a detailed logo would take a lot longer.

There are various ways to do this, though in your case I'd just knuckle down and spend a little while doing this, if you're proficient with any GD software that creates shapes, this shouldn't even take half an hour and if you aren't, now is a good time to learn a few reusable skills.

Also Save for Web & Devices..

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  • Okay. Yeah I'm not really "proficient" in any GD software except GIMP which I guess doesn't do vectors. Anyways, thanks for the help.
    – Jacedc
    Jun 26 '13 at 21:52
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    Photoshop has vector tools but "doesn't do vectors" either in reality.
    – Scott
    Jun 26 '13 at 21:54
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    @Dominic Yes, within Photoshop and ONLY within Photoshop. True vector files can be scaled anywhere.
    – Scott
    Jun 26 '13 at 22:07
  • What do you mean "creates shapes"? It has rectangle and ellipse select (as well as free select and the "paths tool"), but other than that, no.
    – Jacedc
    Jun 27 '13 at 4:04
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    Note that Inkscape is suitable for this sort of thing and is GPL
    – horatio
    Jun 27 '13 at 18:13
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Tracing

In case we can not easily recreate the original in a vector oriented application we may also trace the bitmap to a vector graphic.

Below example was done with Inkscape where I imported the bitmap to trace it with 2 color steps:

enter image description here

This will not preserve the exact circular geometry of the source (note the slightly wavy shapes above), as tracing was done with Bezier curves rather than circles or boxes. Because of that such traces will always have a much bigger file size than properly recreated vectors.

Smoothing

Another possibility to reduce aliasing in a bitmap if we can not use a vector graphic replacement is to apply a soft blur to the image.

Below I used the GIMP plugin GREYC's magic filter: Enhancement - Smooth (mean-curvature) with 8 iterations for smoothing the outlines while keeping the alpha channel:

enter image description here

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  • Hmm. Very nice! I'll take a look at inkscape. Thanks!
    – Jacedc
    Jun 27 '13 at 21:50
  • This link may be better for getting the current G'MIC plugin.
    – EdwinW
    May 12 '18 at 20:12
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There is a really simple way to do this by using the fuzzy select tool to create a path. There is a short example on how to do it at Fixing Jagged Image Edges with Gimp.

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  • The link is dead.
    – EdwinW
    May 12 '18 at 20:09
  • I've replaced the link with a different one that isn't as detailed but does provide the steps needed.
    – David Clarke
    May 13 '18 at 20:18
  • Many thanks, I couldn't figure out which would be a good match for what was originally there.
    – EdwinW
    May 13 '18 at 20:50
  • Let me know how you get on - I can try to find a better option if that one doesn't work for you.
    – David Clarke
    May 14 '18 at 23:10
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For smaller projects, simply using the blur tool can do wonders. While this doesn't apply to this particular project, other people looking may find this solution expedient.

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