Region-based printing quality enhancement

This paper presents a new region-adaptive printing quality enhancement algorithm for mixed scanning documents. To adapt a variety of line-per-inch (LPI) printing documents, novel pixel-wise LPI estimation is done via hadamard transform-based local frequency components analysis. Then, each pixel is classified into either flat-region or edge-region by comparing edge-region representative frequency peak power value and its corresponding flat-region representative frequency peak power value. After, LPI region adaptive-halftone-noise smoother and least square optimal restoration filter enhance the quality of scanned documents. Experimental results indicate that the proposed one provides outperforms other state of the art noise reduction methods on a variety of LPI documents.