or ImageMagick, or plenty of others, with SIMD, GPU, etc. support.

It fills the lightweight niche. You can build it on Windows without needing to drag in all of msys. I can see this as really useful for toy projects and demos.

I'm not sure why walking is an advantage over a hot air balloon. /s

Try to understand that "advantage" can mean different things to different people. Your perspective and usecases might be totally opposite from someone else, and that doesn't mean either of you are wrong.

Both the single header and the zero-allocation callouts can be desirable qualities for something used in an embedded (as in classical MCU-shaped) context.

edit: Seeing that it's also C99 makes me think that embedded applications might be what this was geared toward.

The benefit of single-header, specifically, is that it's super easy to integrate with any project. You don't need to mess with your build system, or the library's build system, just include the file and you're good to go.

No allocation is useful for embedded / resource constrained targets.

easy to test and integrate to your project.

It's sort of like how a clean organized desk is an advantage to some but a hindrance to others....

It's interesting. On embedded, heap allocation is usually not done. If it is, it's permanent- free does nothing. Not always the case, you can enable a real alloc/free algorithm, but usually you don't need to free so it doesn't matter. The stack, though... If you take 2KB of stack and you haven't linked that much in, good luck trying to find that "bug" for why everything gets corrupted/crashes. My point here isn't that 2KB is big for embedded, it's actually that I'd prefer it just either statically allocates the memory or uses the heap so I can at least get an "out of memory" error