comand-line driven image editor

[Hiisi]

Dear Fedora Folks!
I want to write a script that would browse the WEB (Internet shops) and 
using wget will download goods description and pictures. I will parse 
resulted htmls then and represent data into another form (SQL INSERT 
command). I can imagine how to do all that but pictures are the most 
complicated part of the job. I need to change their dimensions and some 
other characteristics, like contrast and brightness. Is there a command 
that will do the task?
Respectfully
--
Hiisi.
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