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Seeing the "canvas color"

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d3zd3z

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  • Real Name: David Brown

Seeing the "canvas color"

PostTue Feb 12, 2019 4:59 pm

Fusion has a notion of a "canvas color". In addition to the DoD, there is a color that is used for pixels that live outside of the DoD. It comes into play when compositing either smaller images, or with transforms that make some of the image not visible.

Normally, this canvas color is all black, with a 0 alpha, but some image operations will change it. For example, the color corrector's offset seems to change the color values, and inverting the alpha can result in the alpha being set to 1. I eventually discovered the "Set Canvas Color" node which can be used to set the canvas color back to black with 0 alpha (sometimes, you can also use a different edge mode).

What I haven't figured out is: is there a way to view what the canvas color is in a given image? Yesterday, I spent a good amount of time trying to figure out what had made an image's alpha become 1, and I still don't quite know where it is happening.

Thanks,
David
MacOS/Linux, Divinci Resolve 16, Fusion 16.
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Bryan Ray

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Re: Seeing the "canvas color"

PostTue Feb 12, 2019 11:44 pm

Just put your mouse pointer in an area outside the raster and look at the status bar at the bottom of the screen.
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Bryan Ray
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d3zd3z

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Re: Seeing the "canvas color"

PostWed Feb 13, 2019 3:50 pm

Perfect, thanks. That seems so obvious now. This was after several hours of trying to figure out what the "canvas color" was even called, so that I could find the node to fix it.

It turns out that my luma key was the culprit, and its output had an alpha of 1.0, with black as the canvas color.
MacOS/Linux, Divinci Resolve 16, Fusion 16.
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Bryan Ray

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Re: Seeing the "canvas color"

PostWed Feb 13, 2019 5:01 pm

Yeah, I do that all the time. Quick fix is to mask the Luma Keyer with the same image you're keying. That way nothing out of raster gets inverted.
Bryan Ray
http://www.bryanray.name
http://www.musevfx.com

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