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I have a big image 5100px x 7000px. I have made the background transparent, and I am satisfied with the result: the parts of the image which I wanted to keep are there, and the white background is gone.

But I am sure there are some pixels, here and there, that are lost in the huge transparent background: pixels which where not pure white, but that anyway should be removed. I can not see them when zooming to see the full image, so I would have to zoom in and scroll around the image to find those unwanted pixels manually. This is very inconvenient, because my screen is not very big, and it will take too much effort to find those lost pixels.

Is there a better way? Is there a way of telling gimp: "show me where are the isolated pixels"?

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1 Answer 1

up vote 8 down vote accepted

There is a very fast and efficient method to remove single pixel noise from a transparent background shown in this example picture:

enter image description here

  1. Use the fuzzy select tool to select the fully transparent background with following settings:

    • Select Antialiasing
    • Select Feather Edges
    • Adjust feather radius to include the size of all noize pixels.
    • Tick Select transparent areas
    • Adjust Threshold to include all of your background (but none of your image).

    enter image description here

  2. Press Del (or choose Edit > Clear) to remove everything from the selected area to make it fully transparent.

    enter image description here

The usual despeckle/denoise filters will not lead to the desired results as these filters will merge the pixel color with the background (which may not be desired).

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Great technique! –  jeckyll2hide Nov 5 '13 at 15:01

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