questions about hex code shown in hex editor

Question

I am stuck on HEX(intel hex) format which I see in Hex Editor (Hex Editor Neo). Ok,I know hex,decimal,binary,their addition,multiplication,their conversion.

Ex. sample.jpg (this is a jpg file I open with Hex Editor Neo in hex format with 4 columns)

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ff d8 ff e0
00 10 4a 46
49 46 00 01
01 01 00 48
00 48 00 00
ff db 00 43
00 05 03 04
04 04 03 05
04 04 04 05
05 05 06 07
0c 08 07 07
07 07 0f 0b 
0b 09 0c 11

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I see this(these are just some of the rows from the whole file) type of hex code. I am interested in what they mean? I know ff d8 ff e0 tells you jpg. I know jpg ends with ff d9. I want to know about other codes..I mean why they are their?.They must be having some meaning or how the conversion takes place from picture to hex.

What do you mean by "4a 46 49 46 00" and many others present there?

Answer 1

Some of it will be standard header information and a lot of it will be picture data. Don't forget that this is a binary file and as part of the compression algorithm the picture file will be converted into a different type of binary encoding to what it originally was. I doubt if you would be able to tell what the picture looks like by reading the binary data that relates to it :)

You can read all about the jpeg standard here.

BTW. hex is just a means of representing the binary data in a more easily understood form than binary. The data is the same - its binary data. If you opened the file in an editor supporting octal it would look different again.