Here's a python-based program that uses Python Imaging Library to manipulate images and renders varieties in differing brightness levels. This program reads an image file e.g. adesdesk_logo.jpg, it splits the read image into its component RGB bands, and generates five channels of varying intensities of this image. The whole body of code can be refactored to collapse all five "for loops" into one I have done this elsewhere, but I maintain a copy of this code as it is still. It is a remembrance of what I came up with in a practice excercise during my earliest days of in python programming.
Yours truly, Adesdesk.