Thanks, I agree with having accessible tools to dissect binary file formats. I'm not sure what you mean by "decided not to parse any metadata", care to elaborate? I implemented the parsing of almost all native PNG metadata chunks because they're concisely described in the official specification. I currently don't parse iCCP or eXIf because they will require reading more long external specifications. I don't parse IDAT (but might soon) because decompressing all the image data could use enough CPU time to have a perceptible lag.