ChromaKeys is a program which is used to quickly remove or mask portions of an image.
Chroma keys may be used for a variety of purposes including :
background removal for photographs
general purpose image masking
icon generation
cutting out portions of an image
creating irregular shaped images
People often spend hours trying to remove a background from a photo, meticulously creating Intricate shapes only to end with dissapointing results.
The movie industry solved this problem by developing blue screens (and later green) screens. Using this method, actors (in the foreground) are filmed against a uniform blue background. The blue background is later electronically replaced with either another image or video.
Using the same exact method with a standard photo can be problematic. The background is almost never "uniform" (unless the photo is taken in a studio or controlled environment - even blue skies tend to darken at the top and lighten towards the bottom). Very often we find colors similar the chroma key may be present in other sections of the image, resulting in undesired areas of the image being replaced.