Abstract: Aiming at the impact of degradation of document image on its binarization, this paper presents a binary image algorithm based on contrast enhancement and background estimation, which is used to binarize the degraded document image. The algorithm uses the different contrast enhancement algorithm to enhance the document image according to the difference of the luminance information of the different sub-regions. The background of the document image is removed by processing the enhanced document image by using a morphological closed operation, and the binarized image of the document image is obtained by combining the Ostu and Sauvola algorithms. The broken handwriting repair is performed by the distribution of the neighborhood of the edge pixels gray value.The experimental results show that the F-Measure （FM） is 90.47%, the peak signal-to-noise ratio （PSNR） is 19.15dB, the negative rate index （NRM） is as low as 0.0538, and the classification error measure （MPM） is reduced to 0.00033. The validity of the binarization algorithm proposed in this paper is verified.

Key words: degraded document； contrast； background estimate； binarization