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After compressing my sale poster, the text and price have fuzzy halos around the letters. How do I fix it?

Switch the output format to WebP, or raise the JPEG quality to 85 or 90, then zoom into the text in the preview until it looks clean. JPEG handles hard edges on flat colors badly, so at low quality it scatters specks and halos around letters and numbers. And remember that a flat-color poster saved as PNG may already be small.

Published · 3 min read

Where the fuzz comes from

JPEG splits the picture into small blocks and simplifies the fine detail inside each one. In photographs you do not notice, because colors blend smoothly. On a poster you have a sharp white letter on a flat red background, and that sudden jump is the hardest thing for JPEG to store. The result is a halo of specks around each character, most visible on thin strokes, Arabic dots and the small digits of a price.

A test on a sale poster

Worked example

A 1080×1080 test poster with a red background, large white text reading 'SALE 30%' and a yellow band with the price 'SAR 149', 71.4 KB as PNG. Results in Chrome:

JPEG at quality 60: 32 KB, 55.1% smaller, mean pixel difference from the original 1.433.

JPEG at quality 88: 51.5 KB, 27.8% smaller, mean difference 0.694.

JPEG at quality 95: 69.8 KB, only 2.2% smaller.

WebP at quality 80: 19.6 KB, 72.6% smaller, mean difference 0.9.

The mean difference is the average gap per color channel on a 0 to 255 scale; the lower it is, the closer the image is to the original. Notice that WebP at 80 is smaller than JPEG at 60 and closer to the original as well. For this kind of design, WebP wins on size and cleanliness at once.

How to fix it

  1. Go back to the original poster exported from your design app, not the damaged compressed copy.
  2. Add it to the Image compressor and choose WebP at quality 80.
  3. Zoom the preview into the price and the smallest text, looking for specks around the letters.
  4. If the platform you post on does not take WebP, choose JPEG and raise the quality to 85 or 90, accepting a smaller saving.
  5. Compare the output size with the original. If the saving is only a few kilobytes, post the original PNG.

Tips for your next promo designs

  • Export posters from your design app as PNG; it keeps text crisp, and for simple designs the size is reasonable.
  • If you need a smaller file, compress from that original PNG, once.
  • Avoid compressing a screenshot of the poster, which adds blur before you even start.
  • If you need the poster in another format without compressing it, use the Image format converter.

Common questions

Why was the PNG small to begin with?

PNG is excellent at areas of a single color and stores them in very few bytes. Photographs are what make PNG heavy.

Does the fuzz appear in product photos too?

Much less, because their colors blend smoothly. It shows most on logos and text laid over the picture.

Does the poster's size in pixels change after compressing?

No, it stays 1080×1080, or whatever your design's dimensions are.