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Text is grainy when i save it

Mar 2, 2012, 20:53
Post: #1
Text is grainy when i save it
Hey all!
My text sometimes is grainy when i upload my graphics to the web and Facebook. Pointers? Looks great when i save it in GIMP. Any help appreciated. I attached a screenshot


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Mar 2, 2012, 21:30
Post: #2
RE: Text is grainy when i save it
The whole image is grainy but it is more visible on the text. Look at the girl in the top right corner... Although saved here at 100% quality, this pic obviously had a previous life as a low grade JPEG(*) and the "grain" is due to compression artifacts. Saving it has a high-quality JPEG won't improve it, it will just faithfully save the artifacts.

(*) looks like it dates back to the late 90s, given its style...

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Mar 2, 2012, 21:51
Post: #3
RE: Text is grainy when i save it
ok well let me try and rephrase the question, is there a way to improve the way your text looks when posting to Facebook or web? w a jpg? i've posted some png's that look very clean
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Mar 2, 2012, 21:53
Post: #4
RE: Text is grainy when i save it
Also, here is the image off of the web... thanks


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Mar 2, 2012, 23:16 (This post was last modified: Mar 2, 2012 23:22 by ofnuts.)
Post: #5
RE: Text is grainy when i save it
So, your "grainy" image is 50% bigger which means it has been enlarged. On the whole, on bitmap images, this should be avoided (one usually works on a large "master" image, and reduces it for some purposes) because the additional pixels are interpolated. This is never good, but some interpolation algorithms are better than others (but the always work better (read: their misses are less visible) on "natural" images (photos, scans of paintings) than on computer graphics (text and logos). The default algorithm in Gimp is "cubic" but it's not the best which is Sinc/Lanczos. Scale tools (Scale Image/Scale Layer/) let you specify the interpolation algorithm. You can also set a Gimp-wide default: "Edit/Preferences" -> "Tool options/Scaling". This is what plain Sinc/Lanczos produces:

[attachment=981]

You can compare with what "Cubic" produces. This image is an "enhanced" difference between the two. You can see that the difference is mostly marked around text (the text, with its green outline, if very difficult to upscale).

[attachment=982]

Finally, you can enhance the Lanczos by re-sharpening it. Here it is after applying "Filters/Enhance/Unsharp mask" with the default values:

[attachment=983]

Also, since text is quite easy to rework, a good solution would be to mask out the existing text in the enlarged version and recreate text with a 50 % bigger font.

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