That’s kind of a niche use-case.
It’s really simple to use a ready-made PNG loader like Python’s Pillow, Rust’s image, Qt’s QImage, GTK’s GdkPixbuf, SDL’s SDL_image [2], OpenCV’s imread [2], etc. and then write out the pixel data in the format you want.
…and, as a bonus, it’ll take PNG input from any tool you want, not just Pixelorama, and will usually accept other image formats too.
(All those links point to the documentation for how to access the raw pixel data with the given library.)
I don’t have personal experience with them, so I don’t know which to recommend, but similar ready-made PNG decoders exist for Lua, Node.js, C#, Java, Free Pascal, Free Basic, and just about anything else you might be working in. (With PHP being a notable pain point because their default “expected to be there” image routines wrap the C API for libGD but don’t provide a replacement for “just dereference the pointer to get the image data”.)
GDScript and QB64 [2] appear to come with PNG loaders as standard.