And here, imitating the "Medium" Convert Size (Quick Action option) chosen in your GIF (which corresponds, I think, to scaling the longer edge of your image (assumed for the moment to be PNG) to 640 pixels:
Medium sized copies (longest edge 640) of selected image files.kmmacros (4.3 KB)
FWIW my impression is that the Finder's convert size Quick Action options correspond to these scalings:
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Small: The longest side of the image is resized to 480 pixels.
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Medium: The longest side of the image is resized to 640 pixels.
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Large: The longest side of the image is resized to 1280 pixels.