title: Equalizing luminance, brightness and contrast for a set of images
body: <p>I use MATLAB for a series of experiments where each eye gets stimulated with a different motiv from the images (binocular rivalry), like on the one is a bottle, on the other a watch.
  There is a Toolbox to adjust the luminance and spatial frequency (Shine toolbox), but that does not work for images where the background is simply transparent, like .png/.tif/.bmp etc. Moreover, the background which shall stay transparent gets included in the analysis and matching routine so that the objects in the center of the image still are not matched perfectly.</p>
  
  <p>Is there a straightforward method in MATLAB (or GIMP) to match the three quantities (luminance, brightness, contrast) in a set of greyscale-images? 
  In GIMP I tried to do it via "Levels", but with unconvincing outcomes, since the histograms of each image are pretty different. Is it possible to setup a predefined template histogram according to which all other images can be matched to get them the same for the three quantities?</p>
  
  <p>Thanks in advance!
  Dalibor</p>