  We propose an algorithm for separating the foreground (mainly text and line
graphics) from the smoothly varying background in screen content images. The
proposed method is designed based on the assumption that the background part of
the image is smoothly varying and can be represented by a linear combination of
a few smoothly varying basis functions, while the foreground text and graphics
create sharp discontinuity and cannot be modeled by this smooth representation.
The algorithm separates the background and foreground using a least absolute
deviation method to fit the smooth model to the image pixels. This algorithm
has been tested on several images from HEVC standard test sequences for screen
content coding, and is shown to have superior performance over other popular
methods, such as k-means clustering based segmentation in DjVu and shape
primitive extraction and coding (SPEC) algorithm. Such background/foreground
segmentation are important pre-processing steps for text extraction and
separate coding of background and foreground for compression of screen content
images.
