Abstract: An image processing apparatus and method which can be selectively used in a variable mode and a fixed mode. In the variable mode, the quantizing values and thresholds for converting high valued image gradation into low valued image gradation can be changed so as to vary the surface gray levels of a printable image at a fixed laser gradation value. In the fixed mode, constant thresholds and quantizing values are used. The use of selectable operation modes enables easy printing operation with increased quality. Also, constant quality of printable images despite environmental changes may be realized by sensing and comparing currently read reference data with initially stored reference data and subsequently correcting quantizing values and thresholds in accordance with the compared result.

Abstract: The present invention is made to reduce the effect of variation of pulses for driving a printer when recording image data and to improve the gray level representation of picture images to be printed. Data incoming through an image reading device are quantized and processed two pixels at a time by a gray level image processing circuit. The two-pixels' data are first discriminated by an edge discriminator to determine whether they represent an edge portion within the image or not. An object image, on which an operation for inter-pixel spacing shall be conducted, is selected according to the discrimination result. The arithmetic and logic portion performs the above-mentioned operation by two pixels at a time if the data correspond to a non-edge portion and performs correction for enhancement if the data correspond to an edge. This may eliminate the effect of dot displacement due to variation of drive pulses of a printer and improve the quality, in particular, of a gray level image portion.