Digikam offers great integrated tools for easy correction of photos. Maybe we should study the interface of these tools:
Section 2.3.4 teaches color correction:
The section explains how to read color curves. Color curves show the distribution of RGB colors. When flat colors are well distributed and the photo is well exposed. When over-exposed, the curves have a right distribution.
Section 3.2 photo workflow
1. Exposure: White Balance
2. Color: White Balance
3. Black and white points: White Balance or Adjust Levels
4. Contrast: Adjust Curves
5. Saturation: White Balance or Vivid or Hue/Saturation/Lightness
6. Resizing (interpolation) : Change Size
The process is the same for video adjustment.
Also digikam uses liblensfun, a library to correct lens errors. I don't know how it implemented in the interface, but many cameras suffer from lens distrotion. The interface seems to be described in Perspective Adjustment, section 18.104.22.168
All that needs to be implemented at MLT level. GEGL could provide the underlying treatment for MLT. I had a look at digikam SVN. It seems very actively developped and very well organized in code. I will ask advide to digikam developers and will get back with the URL of the discussion.