Editing a picture file in code

[BPMan]

i want to edit a picture file with a program. For example i want to go through each pixel and check its RGB values and do something like

if(pixel[123][100].Red == 5)
pixel[123][100].Red = 27

is this possible or is there an easier way to do this.
Thanks

 

[smgarth]

Before you ask a question like that, you need to thoroughly read and understand the specification for the image format you have to decipher (wotsit.org has some decent specs on many file formats, by the way).