What’s inside a PNG file? Graphics, sure. But how is that graphic encoded? [Evan Hahn] shows you what goes into a single black pixel inside a 67-byte file. Why so many bytes? Well, that is ...

A PNG image that requires 198 bytes grows to a much larger 4.7kB file when saved over an existing image. When saved as a new file, it increases by only 56 bytes, probably adding some metadata.