Matrix of pixels from/to an image file

[José Romildo Malaquias <romildo uber com br>]

Hello.

Please, point me to an easy way of obtaining the matrix of pixels
from an image file (in any common format, like jpeg, png or xpm)
and the reverse, given the matrix of pixels, write it as an
image file.

I am programming in C/C++ for Linux with Gtk+.

Romildo
-- 
Prof. José Romildo Malaquias               Departamento de Computação
http://iceb.ufop.br/~romildo       Universidade Federal de Ouro Preto
romildo@iceb.ufop.br                                           Brasil
romildo@uber.com.br