https://netpbm.sourceforge.net/doc/ppm.html (PPM → Portable Pixel Map)

P6
width height
255
<raw RGB bytes>

Ray Tracing In One Weekend (https://raytracing.github.io/books/RayTracingInOneWeekend.html#outputanimage | The PPM Image Format)

https://github.com/qiekn/raytracing/blob/dcccceb9f9fb5da6ea7619169f29a9f76e5688bc/src/main.cpp#L1-L25

• In Jai

https://www.youtube.com/watch?v=xNX9H_ZkfNE

(Here. What is relevant is understanding what exactly you are doing and how to generate pixels. Once you know how to do that, you can actually work with any API.)