1. "I know compositors will apply all sorts of color manipulations to "utility" channels. Adjusting contrast of an alpha channel is often used for making edges look harder/softer. Color manipulations on Z channels are also pretty common. A contrast function on Z buffers is effectively a geometric scaling in the scene along the camera Z axis."
In that case I vote for this too. We have more cases now where contrast can be applied: Case1: grayscale image Case2: color image Case3: utility channel (which can be alpha, z, etc.) Case3 basically means the image has only one channel and we don't care what it is. Am I missing something WIll? 2. "Well, okay, I misquoted the phrasing, but you are still saying that there are "exactly 3." That's what I was referring to." Ah sorry. I see what you refer to, you want to make it general. Agreed. We will have to be careful with handling all the cases though. 3. "Honestly, I'm not even sure if something similar may already exist in OIIO. I have to admit, I've never found the time to familiarize myself with the internals the way I had hoped. My own use of the API barely scratches the surface. The idea of channel masks is inspired a bit by Nuke. In Nuke, you have checkboxes for which channels you want a filter to effect, so you can blue only red and blue, but leave green and alpha alone. Then adjust the brightness of just blue and alpha, etc. It's very flexible. (Though, Nuke thinks in terms of layers of only up to 4 channels, with an arbitrary number of layers. OIIO seems to be slightly more flexible with handling arbitrary numbers of channels.)" This would be amazing to have. I think we can get this with: 1. What you suggested, contrast can be applied to one channel no matter what it is. 2. A general function, apply_operation (contrast, R, 2). contrast is our function which as I said in 1) it can be applied to one channel. R is input/output image and 2 is which channel we want it applied. You think we got it this way? Thanks a lot WIll!
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