READING BITMAP DATA

Hello everyone,

i would like to know how i can write a simple programme in jitter
in order to read the actual data that is written in a bitmap image file (or jpeg, tiff...)
so i guess it would appear as a set of numbers.

I dont want to see the actual image but what the computer writes inside the file.

I know it is a very simple question, but it has been i while that i am trying to find on internet or around me how to do this.

thanks by advance.

arash