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An older 90s mac paint program implemented a black-and-white image scaling algorithm that for lack of a more precise description, "preferred the black pixels" over the white. A consequence of this is that if you were to shrink a drawing too small, it inevitably turned into a black blob. It was nice because it preserved the line art in drawings and 1px lines even when shrunk slightly. In contrast, a naive resizing algorithm would tear apart drawings and line art by interspersing the black line art with white pixels (the nearest neighbors, when sized down).

I'm thinking it's something vaguely along the lines of nearest-neighbor resizing, ANDing the pixels (1 && 1 = 1, 1 && 0 = 1, 0 && 0 = 0).

Is this implemented in any modern-day graphics package like imagemagick or the like, or as a photoshop filter, or even a convolution matrix? Seems like a simple concept, but I can't find it for the life of me.

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    Hi. Welcome to GDSE. This is pretty hard to answer without at least seeing some kind of example. You are basically asking us to try to find something that will do an edit that you once saw in some 90's editor, and that we do not have access to. What are you actually trying to achieve? What issues are you having? There may be a way to achieve what you want without trying to reinvent some kind of resizing algorithm. At the moment, your quesiton reads like an XY Problem
    – Billy Kerr
    Oct 23, 2023 at 10:37

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So you want to resample a black and white image with a round-off bias.

You can easily do that by scaling the image as grayscale (This will introduce grey pixels at edges). To round it off to black or white with a controllable bias to either, just use a threshold filter.

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