How to remove jpeg image compression artifacts?
How can I remove the JPEG artifacts in an image of flat-color background, text and some smaller images? (It's a kind of poster). I have to preserve the text readability.

Can I do that in Gimp or other free image editing tool? I tried to experiment with some of the filters in Gimp, but with no good result (it got even worse).
How to remove jpeg image compression artifacts?
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How can I remove the JPEG artifacts in an image of flat-color background, text and some smaller images? (It's a kind of poster). I have to preserve the text readability.

Can I do that in Gimp or other free image editing tool? I tried to experiment with some of the filters in Gimp, but with no good result (it got even worse).