Kokusai Denshin Denwa Kabushiki Kaisha

Satoshi Katsuno

Atsushi Koike

Yoshinori Hatori

Toshiaki Endoh

It is sought to provide a coding apparatus which permits high efficiency coding of bi-level images with black-and-white pixels halftoned with error diffusion algorithm. An image input/pixel selection unit selects, from an input image as a bi-level image with black-and-white pixels halftoned with error diffusion algorithm, first selected pixels with respect to a pixel '?' to be coded and second selected pixels as peripheral pixels with respect to the first selected pixels. The first selected pixels are fed to a pixel pattern binary scale translator for translation into a binary number. The second selected pixels, on the other hand, is fed to a pixel value adder for counting of black pixels. The count is fed to a binary scale translator for translation into a binary number. The binary number outputs of the pixel pattern binary scale translator and the binary scale translator are combined to be input to an address input terminal of a ROM having a coding information table.

Coding apparatus for bi-level images halftoned with error diffusion

An original grayscale image or color image to be coded is processed by a bi-level image mingled still image coding system to produce a differential image. The original image and the differential image are compared for each pixel block. Only those of the pixel blocks for which the bi-level image mingled still image coding system will be more efficient than a natural image coding system are encoded by the bi-level image mingled still image coding system, and the other pixel blocks are encoded by the natural image coding system. The coding method of the present invention is directed to a grayscale or color image containing an area where pixel values undergo an abrupt change, such as an edge of a letter, or a document with multi-color and natural color images intermingled therein. The method of the present invention obtains a less deteriorated coded image even from an image in which the edge area is very blunt, and moreover, the invention permits high efficiency coding.

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Tokyo, Japan

Satoshi Katsuno