The present invention relates to method, apparatus and storage medium for enhancing document image, and method, apparatus and storage medium for character recognition. For enhancing the document image especially half-tone block image and improving the recognition ratio thereof, the block image is segmented into line images, which are subject to noise reduction. Then, based on the connected component densities, the noise-reduced line images are sorted into three types including normal line image, broken-stroke line image and hollow-stroke line image. Based on their types and other properties, the noise-reduced line images are enhanced, generating enhanced line images, which as a whole constitutes an enhanced block image.