No-reference document image quality assessment based on high order image statistics

Document image quality assessment (DIQA) aims to predict the visual quality of degraded document images. Although the definition of “visual quality” can change based on the specific applications, in this paper, we use OCR accuracy as a metric for quality and develop a novel no-reference DIQA method based on high order image statistics for OCR accuracy prediction. The proposed method consists of three steps. First, normalized local image patches are extracted with regular grid and a comprehensive document image codebook is constructed by K-means clustering. Second, local features are softly assigned to several nearest codewords, and the direct differences between high order statistics of local features and codewords are calculated as global quality aware features. Finally, support vector regression (SVR) is utilized to learn the mapping between extracted image features and OCR accuracies. Experimental results on two document image databases show that the proposed method can accurately predict OCR accuracy and outperforms previous algorithms.