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I have an image made up of "pixel blocks" of size 2x2 (so that each block is made up of four pixels of the same color). How can I scale the image by a factor of 2 in each direction so as to reduce each 2x2 block to a single pixel (1x1), without any type of smoothing? My preferred graphics tool is GIMP, but I obviously accept answers based on any tool! /Andreas

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Surely just resizing it normally would do this? As long as you exactly halve each dimension? –  ACarter Mar 1 '12 at 16:07
    
Yes, I just realized that a simple rescaling did the trick, as long as the number of pixels in each direction is an even number to begin with. If it isn't, there is a lot of unwelcome "bleeding" of color shades. That's where I went wrong. Thanks! –  andreasdr Mar 1 '12 at 16:09
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1 Answer

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Even if your original image dimensions are odd, you can avoid blurring when scaling down by selecting "None" as the interpolation method in the Scale Image dialog:

  1. Select Scale Image... from the Image menu.
  2. Select "percent" as the unit in the Image Size section.
  3. Enter "50" as the width and press enter. GIMP will set both the width and the height to 50%, and round them up to the nearest pixel.
  4. Select the interpolation method "None" in the Quality section.

    Screenshot

  5. Click the Scale button.

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Ah, so that was embarrassingly easy too. Thanks for that! :) –  andreasdr Mar 2 '12 at 12:06
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