I have only learnt CNN models back in uni (transformers just came into popularity at the end of my last semesters), but CNN models learn more complex features from a pic, depending how many layers you add to it, and with each layer, the img size usually gets decreased by a multiplitude of 2 (usually it’s just 2) as far as I remember, and each pixel location will get some sort of feature data, which I completely forgot how it works tbf.