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Can anyone tell me what is causing the discoloration around the black areas in the red field in this image and how to correct it? It's not showing up in the source file JPG or PNG in the program but the distortion is happening when the image is uploaded to Facebook.

Does anyone know what the blurring is called?

Example of issue: https://www.facebook.com/photo.php?fbid=1526732314035887&set=a.116222858420180.7249.100000973998590&type=3&theater

It also only seems to be happening in color fields that are hot pink, dark pink, or berry.

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They are JPEG compression artifacts

JPEG artifacts are areas in an image with a blocky or blotchy appearance. JPEG artifacts are the result of an aggressive data compression scheme that discards some image data.

This is known as "lossy" data compression. Several types of artifacts can appear which are discernible and objectionable to the user. These can include noise around edges, blurring, a smeared appearance, color distortion, and/or checkerboard-like blocking in busy regions.

To avoid these unsightly artifacts you should export at a higher jpeg quality, or - especially in this case where your image consists of blocks of solid colour - as a png file.

  • Would love to know what the downvote was for... – mayersdesign May 8 '17 at 10:29
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    Because this is not a good answer in this case. The problem isn't on the user system (Gimp or else), it is Facebook recompressing images, so this answer is slightly misleading and Billy Kerr's answer is much better. – xenoid May 8 '17 at 12:02
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These are JPEG compression artifacts, caused by Facebook when it processes and often rescales uploaded images, and adds more lossy compression. If you follow Facebook's help guidelines for making sure your images are displayed at the best quality, you should be able to ameliorate the problem.

Here's what they say:

We automatically resize and format your photos when you upload them to Facebook. To help make sure your photos appear in the highest possible quality, try these tips:

Resize your photo to one of the following supported sizes: Regular photos: 720px, 960px or 2048px wide Cover photos: 851px by 315px To avoid compression when you upload your cover photo, make sure the file size is less than 100KB Save your image as a JPEG with an sRGB color profile

You can also changes your settings so that your photos are uploaded in HD by default.

Source: https://en-gb.facebook.com/help/118731871603814/?helpref=hc_fnav

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