Abstract: An image data adjusting device adjusts the number of pixels of input image data. The device includes a data adjusting table representing magnifications for all the pixels of the input image data per direction in which the number of the pixels of the input image data is adjusted. The device further includes a data adjusting section which refers to the data adjusting table and copies each of the pixels serially inputted in a scan direction as many times as represented by the corresponding magnification of the data adjusting table, thereby to obtain output image data.

Abstract: An image data adjusting device adjusts the number of pixels of input image data. The device includes a data adjusting table representing magnifications for all the pixels of the input image data per direction in which the number of the pixels of the input image data is adjusted. The device further includes a data adjusting section which refers to the data adjusting table and copies each of the pixels serially inputted in a scan direction as many times as represented by the corresponding magnification of the data adjusting table, thereby to obtain output image data.

Abstract: A continuous-tone image is converted to a bi-level image by first applying an inverse gamma correction to a threshold matrix, then comparing the gray levels in the continuous-tone image with the corrected threshold values. The threshold matrix may be selected from a library of threshold matrices, and the inverse gamma correction applied by using a gamma correction table selected from a library of such tables. Alternatively, a library containing at least one corrected threshold matrix, to which the inverse gamma correction has already been applied, may be stored.

Abstract: A dithering device converts a multi-gradation image into a binary image by comparing, in sequence, values of pixels forming the multi-gradation image with threshold values of corresponding elements forming a dither matrix. For determining the element corresponding to the pixel, the dithering device uses an array representing a relationship between a first group of positions of the elements to be used currently and a second group of positions of the elements to be used next. By referring to the array, the dithering device determines the position of the element from the second group based on the position of the element in the first group so as to compare the next pixel with the threshold value of the determined element.

Abstract: Dither patterns are generated for use in converting a gray-scale image to a bi-level image. The dither patterns simulate halftone screen patterns with arbitrary screen angles. The dither patterns are made up of unit patterns, and have sizes calculated so that the unit patterns match up at the edges of the dither pattern.