A method of document image enhancement based on the combination of CLAHE and detail amplifying
CLAHE和细节放大相结合的档案图像增强方法

The document image incorporating with image enhancement method can achieve a good perceptual quality, which is necessary for the document image information system. Contrast-limited Adaptive Histogram Equalization (CLAHE) is widely utilized to expand the global dynamic contrast range, and Lee filter is usually used to amplify the local details. A detail-amplifying CLAHE (DAHE) method is proposed by combining the above two methods. Firstly, a noise-resist policy is employed to differentiate the detail and the noise. Secondly, a flexibility amplifying mechanism is proposed to make the amplified image suitable for the human vision system. The proposed method can not only balance the global gray-level dynamic range, but also enhance the local details. The experimental results demonstrate that the proposed method can both enhance the document image, which is suitable for the document image information system, and satisfy the requirements of the national industry standard.