Apparatus and method for processing image

Abstract

An apparatus and method for processing an image which are capable of producing a printed image satisfying both resolution and reproducibility of gradation. This method admits as an input the RGB data of the size of one pixel and converts this input into lightness data and density data. When a target pixel is determined to correspond to a non-edge portion, the method performs a computation for finding the remainder,of X/,and the remainder m of Y/,from the coordinates (X,Y) of the target pixel thereby deciding which of the total of nine pixels of a non-edge grade dither pattern is to be extracted, and allocates the position d(l,m) to the extracted pixel. On the other hand, when the target pixel is determined to correspond to an edge portion, an edge grade dither pattern corresponding to the density of the target pixel is allocated directly to the target pixel. The processing of conversion into the non-edge grade dither pattern d(l,m) or the processing of conversion into the edge grade dither patter which is performed as described above is carried out on all the pixels which have been read, depending on the determination of whether the target pixel corresponds to the non-edge portion or the edge portion, and the converted data obtained consequently is emitted.