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Thread: GIMP Pixel Problem

  1. #11
      waldronate is offline
    Software Dev/Rep Gracious Donor waldronate's Avatar
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    Mar 2007
    The High Desert


    If GIMP has a color index mode, make sure that you're not using that. Always try to do this sort of editing in RGB mode rather than color index mode, because the colors that the system may pick aren't necessarily the ones that you'd pick.

  2. #12
    Guild Master Gracious Donor Midgardsormr's Avatar
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    Aug 2007
    Los Angeles, CA


    I'm not familiar with Gimp, but what you're describing is very likely a filtering artifact, as Falconius said. For more information on filtering, read this thread: [Award Winner] Bitmapped Images - The technical side of things explained. Posts 9-13 are the most relevant to this topic.

    In a nutshell, though, if there is a filtering, anti-aliasing, resampling, or interpolation option (all four of those terms are roughly equivalent), you need to set it to either "nearest neighbor" or "none." It may be in the tool itself, or it may be a global setting. That will ensure that the software does not create any intermediate colors when transforming. Instead, it will pick the color of a pixel based on whatever whole pixel in the original shape that fell closest to it after the transform. Be aware that if your lines are less than three pixels wide, nearest neighbor filtering may create holes in the line after a rotation. That could interfere with your ability to bucket fill.

    Based on the description of your workflow, though, I wonder if you might be more comfortable with vector software like Inkscape? Vector objects are not groups of pixels, but are actual shapes that you can manipulate to your heart's content without ever needing to worry about pixelization or filtering. It may take a little bit of time to learn the new tool, but you might find it better matches the way you want to work.
    Bryan Ray, visual effects artist

  3. #13
      Redrobes is offline
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    Dec 2007
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    Sounds to me like filtering - as said, try to use nearest neighbor filtering where you want to preserve the color to an original shade. Gimp may not have an option to set that for an operation like rotation or scaling as part of some other process. Ideally - as per my tutorial - its best to work in a res of 2x or 4x the original and then scale down the final and then its less of a problem. You should also have some options on the match threshold of bucket operation. I dont use Gimp so I cant say but usually paint packages have this. Just up the threshold a bit and it should include some of the pixels which are a shade near to the original.

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