ImageMagick convert: Making viewable copies of underexposed images

This post was written by eli on March 16, 2010
Posted Under: Linux,Software

The problem is relatively simple:  Sometimes I take images that are deliberately underexposed, or such that have important parts in the dark areas. This is then fixed with GIMP. But in order to choose which image to play with, I need to those details visible in some test image, so I can browse them with an image viewer. Playing with each shot manually is out of the question.

My original thought was to use GIMP in a script, as I’ve shown in the past and feed GIMP with some LISP commands so it resizes the image and runs a “Curves” command.

But then I thought it would be much easier with the “convert” utility. So here’s a short script, which downsizes the image by 4 and gives some visible dynamic range. If you want to use this, I warmly suggest to read the ImageMagick manual page, since the values given below were right for one specific set of shots. You’ll need to tweak with them a bit to get it right for you.

The script generates copies of the originals, of course…


for i in IMG_* ; do
  echo $i;
  convert $i -resize 25%x25% -level 0,1.0,16300 -gamma 2.0 view_$i ;

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