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Image Quality Loss

Feb 4, 2012, 06:34
Post: #1
Image Quality Loss
Hi all! I'm working on a book where I need to combine several elements that are created on different programs. I'm able to use the transparency feature to over lay them and combine them but when I save there is noticable quality loss. Am I doing something wrong? The elements are made with ms word, excell and a music notation program. I have been saving them in pdf format so gimp will recognize them. Once I import them into gimp by using "open as layers" then I can go to "layer" then to "transparency" and then to "color to alpha". That brings up the next layer down. Then if I hit "layer" then "merge down" then hit "color to alpha" again I get the next layer. I have managed to make this work and combine up to 5 different elements (layers). But as I say, no matter what format I use to save with, even the native format, there is image loss when I print. Am I doing something wrong? Any advice will be great. Thank you!
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Feb 4, 2012, 10:36 (This post was last modified: Feb 4, 2012 10:51 by ofnuts.)
Post: #2
RE: Image Quality Loss
What you do is typically vector graphics and Gimp is for bitmap graphics. So IMHO you should be using Gimp's cousin for vector graphics: Inkscape. Then where you would import the music and do the rest of the graphics (shapes/text) directly with that software.

If you stay with Gimp:
  • For decent printing of this kind of graphics, you need 300 pixels/inch, which means that you should be handling pictures that are at least 3000 pixels on the long side for standard paper sizes (A4/Letter: 10-inches high printable area).
  • With you current method the anti-aliasing pixels on the top layer are subjected several times to color-to-alpha, and this "erodes" them. In fact in Gimp you very rarely need to merge layers, and they are best kept separate since this allows further changes and second thoughts. So just use color-to alpha on each layer in turn. Merge will be happen when you export/save to a "flat" format. Otherwise if you need one single layer (but then I'd be curious to know for which purpose) then merge all your layers once (or better, use "Layer/New from visible")

Now answering your questions on
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