Automatic trimap extraction for efficient alpha matting based on gradient field transforms

Image/Video Matting aims at solving the problem of accurate foreground estimation from a given background within still images or video sequences. The standard alpha matting method starts from a trimap, which separates an input image into three regions: definitely foreground, definitely background, and unknown regions. This paper presents an automatic trimap extraction based on an affine transformation of gradient fields in order to achieve an improved and robust Image/Video matting method. A gradient field based background and foreground segmentation technique provides a trimap extraction, which is robust to changing light conditions within semi-transparent objects. Our proposed background subtraction is based on affine transformed gradient projections of the input and background image and removes the background texture from a given image, preserving the texture of the foreground objects. The presented automatic trimap extraction method reduces the manual labor work in extracting and embedding target objects into a new background image or video sequences and might find its application within the broadcasting or movie industry.