Abstract: A half-tone image is produced by scanning a plurality of input points of an original, outputting a screened image having a plurality of black and white dots and transmitting signals representing the screened image to a marking device. The size of each plurality of dots is determined from a recursive relationship between a value of a current input point, a previous output and an error representing a difference between a value of a previous input point and the previous output.

Abstract: A motor rotational speed control apparatus is constructed by a control unit for performing an instruction to accelerate a rotational speed of a motor, an instruction to decelerate, or an instruction to maintain a rotational speed, a driving unit for driving the motor in accordance with an instruction outputted from the control unit, and first and second wires for transferring the instruction of the control unit to the driving unit. The control unit shows the instruction by a combination of signal levels of a first signal and a second signal and transmits the first and second signals to the driving unit through the first and second wires, and the driving unit drives the motor in accordance with the combination of the signal levels of the first and second signals.

Abstract: An image treatment apparatus comprising: an input device for inputting image data; a setting circuit serving as a reference when the image data is quantized in accordance with the image data input by the input device; a quantizing circuit for quantizing the image data; and a device for outputting an image in accordance with the result of treatment performed by the quantizing circuit, wherein the quantizing circuit performs the quantization by correcting the error between the image data input by the input device and the image output by the outputting device.