zoomenhance
the Mars anomalies image viewer with realtime enhancements
...The region of interest depends on zoom-factor and dimensions of the output window.
The special second version of this filter adjust the contrast independently for any R,G,B layer. This maximizes the visibility of color differences. For example: very useful for images from the Mars-rovers with reduced contrast and color information.
More realtime functions: brightness, contrast, gamma, RGB/HSL, un/sharp, unblur.
You can find configuration notes here in the wiki.