Inspired by a stream from @rexim.

First, make data dirs, e.g.:

$ ls data/
cifar-10-batches-bin/  mnist-raw/  output/

Next, adjust config.h accordingly, then:

make && ./main

You can view the images, e.g. using feh:

feh -g 512x512 -Z ./data/output

• MNIST
• CIFAR-10

stb_image_write.h and stb_ds.h from https://github.com/nothings/stb.