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F-Spot had an "enhance" button that magically turns the image on the left into the image next to it (see below). It worked brilliantly for quite a range of images. Unfortunately it has problems, and I'm not using it for photo management any more.

Does anyone know of a similar excellent "enhance" function? The one in Shotwell is useless.

enter image description here

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3 Answers

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If you use the GIMP, the toolbar menu has an option for Colours->Auto->Equalize. I tried it on your "before" image and the "after" result was almost identical.

Also GIMP would give you more control over adjusting colour curves/contrast/etc. manually if you prefer.

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You're right! It does better than ImageMagick on the top half, but still slightly worse than the f-spot version. I'm sure it's possible to improve that manually, if you know how. –  Jean Jordaan Dec 25 '11 at 10:10
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If you are on the command, line I recommend that you use "convert", a command from the ImageMagick Package. try:

$ convert -enhance -equalize -contrast image.jpg image_enhanced.jpg
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Hey, that's not bad at all! The bottom half of the image comes out better, in my opinion. But the top half of the image comes out worse :-p I'll update the answer to show all three. –  Jean Jordaan Dec 25 '11 at 9:46
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When trying to enhance the visibility of details in an image where some regions are low-contrast, I found none of the single-step solutions in ImageMagick or The GIMP satisfactory. (XV used to have a great button, but is non-free and hard to obtain now.)

But the following process produced the kind of results I wanted. It simulates a high/medium pass filter in The GIMP.

http://www.gimpusers.com/tutorials/equalize-homogenize-brightness

  1. Do Layer -> Duplicate Layer
  2. In the Layers Window (Ctrl-L) be sure the upper copy is selected
  3. Do Filter -> Blur -> Gaussian Blur with a medium size radius (e.g. 25)
  4. Do Colors -> Invert
  5. Do Colors -> Desaturate -> (Lightness)
  6. In the Layers Window (Ctrl-L) set the Mode to "Overlay"
  7. If satisfied, do Image -> Flatten Image. Otherwise undo to step 2 and try again with a different blur radius.

You may see a visible "halo" around dark elements, or "shadow" around light elements - that is it working!

Better results might be obtained by combining a number of layers with different blur radii.

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