This filter is for simple manual color adjustment by RGB channel, either through adding constants, or changing the channel gammas or gains.
means that it works channel-wise, no crosstalk. The off-diagonal elements of the transform matrix are zero - no color crosstalk, no color space rotation. But this should be sufficient for many tasks. For example, when shooting under tungsten light, the blue signal will not migrate into red, it will simply be too small. Amplifying the blue (and a bit of green too) should be all that is needed. Similar, an underwater shot will simply be red deficient, needing some red boost, etc.
- These determine the change in each of the three color channels.
- adds a fixed value between -150 and +150 (this is sometimes called "black level" or "setup").
- changes channel gamma between 0.3333 and 3.0.
- multiplies channel with a value between 0.3333 and 3.0 (sometimes called "gain" or "contrast")
To visualize this plugin's actions, apply it to a gray gradient, and watch the result with "pr0file".
- Keep luma
- Fixes the luma value, so that the sliders only affect color.
This is the frei0r filter coloradj_RGB