Multiple instances of keyers can be stacked, or you can color correct the shot to maximize the chroma area, key the shot, then use the keyed shot as a matte for another copy (so preprocessing doesn't affect final color. Many keyers, Hitfilm's included, have spill suppression, feathering, threshold controls.
I'm curious how you think such code would be written? Remember, the computer has no idea what an image contains in terms of "content," it's just looking at pixel values, and the keyer is removing anything within the threshold of the designated values.
Can someone tell me if there is something I can click on that will do this? I have all the latest versions of Hitfilm and Ignite, and I work on a Windows 10 machine. It seems so obvious to be able to selective apply a chroma key effect to only part of a video layer, but I can't figure out a way to do this. Moreover, if I duplicate the layer, apply the chroma key effect to the top layer, and then apply a garbage mat to the bottom of the chroma keyed layer to let the pants come through as background from the lower copy, I run into the problem of not having the coloration match completely if I use any of the color adjustment tools of the chroma key effect. If I use a garbage mat to crop the pants, I will lose the pants in the video. I want to apply a mask to the image that will apply only to the area chroma keyed, without affecting the rest of the image. Let's also say that the person made the mistake of wearing green pants to the shoot. Let's say that I have a person sitting, and there is a green screen behind the person above the shoulders. Is there a way to selectively apply a chroma key effect to an image? I am not talking about using a garbage mat.