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Transform Node Messes Up Alpha Channel Manipulation
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Description

System Information
Arch Linux
Nvidia 750ti

Blender Version
Broken: 2.79 (Tried 2.8 as well and I have the same issue)

As referenced here:
https://blenderartists.org/t/filters-unintentionally-crop-transformed-image/1132477/4

When I take an image in the compositor and scale it up 2x or whatever and then separate the RGBA and dilate/erode the alpha and use that to set the alpha on the image, it only works within the size of the original image and not the scaled up image. Also even if I use the R, G, or B, it still only uses the size of the original image and not that of the scaled up one.

Cropped if I try to mess with the alpha after a transform.

Uncropped if I mute my changes to the alpha.

Also I believe that if you scale down

Details

Type
Bug

Event Timeline

Philipp Oeser (lichtwerk) triaged this task as Normal priority.Nov 7 2018, 3:04 PM

I guess this is known limitation of the compositor (but I am not sure).
Workaround is (as you said) to first do the erosion first, then the scaling.

@Jeroen Bakker (jbakker), @Brecht Van Lommel (brecht) : could you comment? [not sure if we can close this as a "known limitation"?]

Working around it would be easier if the dilate/erode node had an input for step value.