JPS5713858A - Adaptive quantization device - Google Patents

Abstract

PURPOSE:To make an adaptive quantization device follow up the whole level variation of input picture signals, by expressing an area varying in density from thick to thin by using less bits than those of uniform quantization and fixed quantization, by quantizing picture signals by using an adaptive quantization device. CONSTITUTION:The 1st quantizing circuit 22 quantizes the brightness levels of picture elements from sensor 21 and the quantized brightness levels are stored in a memory circuit 23. The contents of this circuit 23 are read out during a blanking period between the main scanning of some line and that of the next line and counted by an address counter 24, thereby detecting the brightness level when its count value has a maximum value by a mode detecting circuit 25. A mode detected by this circuit 25 is compared with the reference level of the last line stored in a reference level setting circuit 26, thereby updating the reference level according to the comparison result. The 2nd quantizing circuit 27 converts the digital picture signal from the circuit 22 into a picture signal consisting of a prescribed number of bits, thus following up the whole level variation of the input picture signals.