Threshold selection for text segmentation is an essential preprocessing step in most document processing algorithms. Although there are a number of sophisticatedly well-trained methods for text extraction, many researchers still prefer a fast and simple threshold selection algorithm for preprocessing. In this paper, a new global threshold selection method is proposed based on fuzzy expert systems (FESs). It initially enhances image contrast by using a FES. Then, the range of the threshold value is adjusted by using another FES and a pixel-counting algorithm. Finally, the threshold value is obtained as the middle value of the above range. To evaluate the performance of the proposed algorithm, we employed a database of 20 English, Farsi, and Chinese document images. Experimental results demonstrated that our method provided superior solution quality compared to a number of well-known frequently used counterpart algorithms. The computational burden of the proposed algorithms is actually light with the computational complexity of O(MN) for the image of size M×N.

Keywords