Image signal encoding apparatus

摘要

An image signal encoding apparatus reads an image from an original and converts the image into color data values including lightness and chromaticity components. The data values are stored and divided into pixel blocks with data values of lightness components and pixel blocks with data values of chromaticity components. Average lightness component data values are computed for pixel blocks of lightness components and average chromaticity data values are computed for pixel blocks of chromaticity components. A region determination is made whether the pixel blocks correspond to a color, monochrome or background region in the original based on the average pixel block data values of lightness components and chromaticity components. A switch outputs the lightness pixel block data values during the region determination, and outputs the lightness and chromaticity pixel block data values after the region determination. The lightness pixel block data values are adaptively bi-level connected based on the result of the region determination. A bi-level image encoder encodes lightness pixel block data values converted by adaptive bi-level conversion and the result of the region determination is stored as region information. A color image encoder encodes the chromaticity pixel block data values consisting of mxn pixels determined to correspond to the color region based on the stored region information after the region determination process on the whole original is completed and a transmitter transmits at least one of the set of data values encoded by the bi-level image encoder and the set of data values encoded by the color image encoder.