IMAGE COMPRESSING APPARATUS

An image compressing apparatus has a predictive coding unit, an orthogonal transform unit, a quantization unit, a variable length coding unit, a coding control unit and a start decision unit. The start decision unit receives predictive errors from the predictive coding unit and a quantization parameter from the coding control unit to produce a start control signal. The start control signal is set to a logic value 1 if the orthogonal transform unit, the quantization unit and the variable length coding unit are to be activated, and to a logic value 0 if they are not to be activated. The orthogonal transform unit, the quantization unit and the variable length coding unit are activated with the logic value 1 to perform respective processes, and are kept unactivated with the logic value 0. The image compressing apparatus is low in power dissipation and short in processing time.