How to interpret image hex dump?

Question

I'm curious about how the PC actually sees files, and after I did an assignment about files and used hex dump to check if it was writing correctly, I wanted to try it with other file types (actually I'm just using a Notepad++ hex dump plugin), like images (like, 1 black pixel), in different formats, but I didn't understand very well (like why the black pixel in .gif has so much more stuff than .png or .jpg). Is there anything like a "manual" of some sort to how images (and if possible, any type of file) are "encoded" or "encrypted" (don't know the right word for it)? Or just a hint at what I'm actually looking for so that I can look it up myself? I'm not an image expert or anything, I just know there's gamma, alpha (transparency)...and that's all hehe.

Answer 1

There's no general directory of file type specs, and some of them are not publically documented. JPEG PNG and GIF are, however:

JPEG, file layout is on page 5.

PNG, file structure starts on page 12.

GIF, this one is not as well-written. The "header" section will tell you what the start of the file means, the rest is scattered in the previous sections.

Generally, you can find the specification for a file type by just searching " specification" on Google, and it'll be the first result. Be prepared to do a lot of tedious byte-counting.