Recover a usable alpha channel from images that have none!
This tool is based on techniques used by Windows screenshot tools of yore. Back then, Aero was new and people really wanted screenshots where title bars were see-through.
My use case is a bit different: To this day, Blender's image exporter will not properly export
images that have certain post processing effects applied to them in the compositor.
This is my workaround: By exporting two different versions of a render,
one with a solid black background and one with a solid white background,
this tool will recover a version with an alpha channel that leaves effects intact.
Prebuilt binaries for all relevant platforms can be found here: https://github.com/SamusAranX/realpha/releases/latest
To install realpha from source, clone this repository, then run cargo install --path . inside it.
To run realpha on two input images, simply run
realpha black.png white.png out.png
and it'll generate a new file out.png for you.
Images need to be exactly the same except for the background, this means their sizes and color modes have to match.
realpha currently supports RGB and grayscale images with 8 and 16 bits per channel. Output images will be in the same format as input images. 32-bit, paletted, or animated images are not supported and out of scope for this project.
Click to view images
Input images:
Output image:
