IMAGE COMPRESSING APPARATUS

An image compressing apparatus employs a mean-separated normalized vector quantization method according to which, with respect to vector components corresponding to input images inputted from image sensors via a plurality of lines, encodes and outputs a scalar-quantized code of a mean value, a scalar-quantized code of a maximum scalar product value with each code word in a code book, and an index of one of the code words which yields a maximum scalar product value. In this image compressing apparatus, when the maximum scalar product value is less than a predetermined threshold value, in accordance with judgement by a comparator circuit, an output selecting circuit stops outputting the codes of the maximum scalar product value and of the index, and outputs only the code of the mean value. Therefore, when the image is uniform with pixels varying little in their luminance levels in compression processing unit blocks, code data to be outputted are restricted so that only data of the mean value are outputted. Consequently, it is possible to restrain degradation of the image and to considerably reduce data amount.