1. A method for detecting anti-aliased images comprising: determining a threshold number of unique colors; counting using a CPU a number of unique colors of pixels in an image, and if said number of unique colors of pixels in said image is no greater than said threshold number, determining that said image may be a two-color anti-aliased image; determining two extremal colors of said image; calculating using a CPU if each pixel has a color which lies on a line connecting said two extremal colors in color space, and if each pixel of said image has a color which lies on the line connecting said two extremal colors in color space, then verifying that said image is a two-color anti-aliased image; and in response to verifying that said image is a two-color anti-aliased image, compressing data representing said image as data representing a two-color anti-aliased image to generate compressed data representing said image.