That was the goal, but the underlying library is general-purpose.

Writing a minimal uncompressed PNG writer from scratch is a fun exercise; the spec is pretty clear and the only tricky part, really, is getting the uncompressed zlib part right, especially since the block sizes are undocumentedly little-endian, while everything else is big-endian.

Self-contained code for image generation and consumption can be pretty useful. It's one of the reasons that I like farbfeld, suckless's incredible simple binary image format, because libraries for processing it are essentially unnecessary since the format itself is so straightforward.