Multilevel Rendering of Document Images

Rendering document images for scanning and printing applications typically involves binarization via adaptive thresholding, halftoning, or color dropout. While bitonal rendering is often adequate, there are cases where multi-level rendering is required to capture important image characteristics. In this paper, we present two methods for multilevel rendering of document images. The first method involves adaptive multilevel thresholding of gray scale images based on background tracking. The second method presents color form dropout using color quantization. Both methods are based on a computationally efficient version of the K-means algorithm. The selection of thresholding, halftoning or color dropout depends on the document type and can be applied to the whole image or to various image regions, as determined by a document categorization and segmentation module. Key-Words: Multilevel rendering, color dropout, adaptive thresholding.