Image data processing system with adaptive binary quantization

Abstract

An extractor extracts, from image data to be binarized, a feature amount of a target pixel including at least a maximum density difference among pixels in a local region including the target pixel. A predictor predicts an image type of the target pixel in accordance with a minimum density value among the pixels in the local region. A selector selects one of the feature amount of the target pixel from the extractor and a feature amount obtained by adding the feature amount of the target pixel to feature data of neighboring pixels in accordance with the image type predicted by the predictor. A discriminator discriminates the image type of the target pixel in accordance with the feature amount selected by the selector. A weighting section weights the discrimination result from the discriminator with respect to the neighboring pixels of a predetermined range preceding the target pixel in accordance with distances from the target pixel to the neighboring pixels so as to generate feature data of the neighboring pixels selectively used by the selector. A determinator adaptively determines a threshold value for binarizing the image data in accordance with the discrimination result. A binarizing section binarizes the image data in units of target pixels by using the threshold value determined by the determinator.