Hide Pictures in a Histogram
Anyone with even minimal image processing experience will likely have a good grasp on a luminance histogram– a graphical display of the color range and prevalence in a given image. Most of the time, a histogram should look something like a sine wave mixed with a mountain, but some enterprising hackers have figured out how to do a bit of switcheroo on the image-histogram relationship, creating a mostly content empty image, but visually interesting histogram. [via]
Now there is a php script that will allow you to generate your own gradiant that will make an image in the histogram: http://fisher.spadgos.com/histo/
The next challenge is to take a real picture, and make it look good with a interesting historgram