Wasted many more hours on this so far. There are 2 deleted scenes of Harry and Dumbledore in the cave. Again, they aren't color corrected.
Getting the levels right is easy enough, but I knew there had to be a way to do this right (not just tweaking the hue and desaturating).
After much messing around, I realized individual color saturation/hues was not the answer, but that all they did after darkening the picture was to just pick a color and tint the whole scene.
I found 2 identical frames, one from the theatrical scene, one from the deleted. With a snapshot of the theatrical frame, I used GIMP to find the peak RGB levels. (This is similar to how autolevel type adjustments assume the brightest color is pure white).
With these RGB levels, I converted to Hex and used a nice little AviSynth filter called Tint(). Then I just tinted the frame to match.
Again, not perfect, but it has me impressed.
Deleted Scene (Raw):
Theatrical Frame:
Color Corrected Deleted Scene:
I'll be going back to that hallway scene and redoing it now. It looks like it has orange tinting.
Btw, while messing around I found a really neat avisynth filter called ColourLike. http://forum.doom9.org/showthread.php?t=96308 I didn't use it here, but it could be helpful for others.
ColourLike takes the histogram of 2 video clips, and then applies the histogram of one clip to the other. Might be nice for some Star Wars color tweaking if we had a source we liked the colors in... like maybe a laserdisc.