How to get the width/height of jpeg file without using library?

Question

Firstly I want to say I tried many times to find the answer by using google search, and I found many results but I did not understand, because I don\'t know the idea of read

Answer 1

Image dimensions in JPEG files can be found as follows:

1) Look for FF C0

2) At offsets +4 and +6 after this location are height and width (words), resp/ly.

In most cases, the absolute offsets of height and width are A3 and A5, resp/ly.