ADAPTIVE THRESHOLDING ALGORITHM AND ITS HARDWARE IMPLEMENTATION

This paper presents an adaptive raster-scan thresholding algorithm which can deal with an image acquired under imperfect illumination. A statistical measurement called LSSD (Largest Static State Difference) relating to the gray-level variation is found first, According to the measurement, the pixels are separated into static and transient states which are treated by two different procedures, respectively. A hardware implementation of this algorithm shows that the real-time requirement can be met. Experiments of applying this algorithm to extracting characters from documents confirmed that a reasonable binary image can be efficiently and effectively obtained from a gray-level image under various illuminations.