Own implementation loader/renderer

I've been implementing my own code for loading & rendering PNGs, I've
managed to get the filters correct for 8 bit values (or working
individually, or both) but when I went to test on a PNG made for 4 bit
values and using all filters in one file I get a corrupted image that
resembles the target image, I've made a post about it here:

https://cboard.cprogramming.com/c-programming/180516-final-filter-test-failing-post1302846.html#post1302846

Since the other test images came out correctly I doubt it's my
implementation of zlib but it could also be that, either way I'd like
someone to take a look at my code here:

https://gitlab.com/awsdert/glengine/-/tree/main/view

And tell me if they see anything that would be a problem in regards
defiltering the data

Btw the images I'm currently testing with are here:

http://www.schaik.com/pngsuite/pngsuite_fil_png.html

The one that fails is just the last one that looks like a ball