@retr0id For JPEG DCT is the one thing you just have to accept and then (de)quantization, YCbCr, RLE, delta coding of DCs, canonical Huffman coding, as well as things like MCUs and Marker Segments are things you need to learn but you can successfully explain all of them half-drunk to your buddy in a bar with a pen and a napkin (ok, probably a few for all of it) and get the point across just fine [progressive JPEG, you'll want to defer until baseline is working and you're sober.]