X-Pixmap & NetPBM

Half the code is Tests, all functions are asserted.
Only uses system.nim, no imports, does not use std lib, easy to maintain.
runnableExamples with static: and doAssert.
Documentation with Examples and Links.
Works at compile-time, NimScript and JavaScript.
All functions are func, except 1 that does the I/O.
Tiny func of 3 ~ 5 lines, simple code, simple API.
Functionality can be extended with sequtils by the user.
Examples render 6 small fractals at compile-time to mimic a real-world like usage.
Only ~300 lines where half are test, 5 image formats.

Random example use cases

Generate Icons of arbitrary sizes instead of bundling them in binaries and installers.
Generate patterns on client-side browser instead of transferring them over internet.
Render QR codes, Bar codes, Icons, visual reports, simple diagrams for documentation, etc.
Plot charts with data of any kind on any target.
Anything image related, good addition to SVG and HTML that std lib already can do.

Format

Image format is loss-less and human-readable, UTF-8 but fits ASCII, is also valid C source code, can be embedded in C, supports millions of colors and transparency.