Fast incremental algorithm for speeding up the computation of binarization

Binarization is an important basic operation in image processing community. Based on the thresholded value, the gray image can be segmented into a binary image, usually consisting of background and foreground. Given the histogram of input gray image, based on minimizing the within-variance (or maximizing the between-variance), the Otsu method can obtain a satisfactory binary image. In this paper, we first transfer the within-variance criterion into a new mathematical formulation, which is very suitable to be implemented in a fast incremental way, and it leads to the same thresholded value. Following our proposed incremental computation scheme, an efficient heap- and quantization-based (HQ-based) data structure is presented to realize its implementation. Under eight real gray images, experimental results show that our proposed HQ-based incremental algorithm for binarization has 36% execution-time improvement ratio in average when compared to the Otsu method. Besides this significant speedup, our proposed HQ-based incremental algorithm can also be applied to speed up the Kittler and Illingworth method for binarization. (C) 2009 Elsevier Inc. All rights reserved.