Image processing apparatus involving comparison of densities of three

Abstract

A graphics accelerator decides pixel densities using an anti-aliasing process for left and right edges of a figure in an image, and for sending resulting pixel density data to a frame memory. The apparatus includes a memory read/write controller inputs a contribution ratio, a density value, a 'y' coordinate for a raster line, a start coordinate x.sub.1, and an end coordinate x.sub.2, and sends an address to the frame memory. A LUT provides pixel densities based on the contribution ratio and the density value. Three contiguous pixels' densities are latched, including densities for a middle pixel and two outer pixels. A comparing processor, decides a resulting pixel density corresponding to the middle pixel by comparing the densities of the three contiguous pixels, and deciding the resulting pixel density as being an intermediate value between the densities of the two outer pixels if the middle pixel's density is not between the densities of the two outer pixels, but deciding the resulting pixel density as being the density of the middle pixel if the middle pixel's density is between the densities of the two outer pixels. Identification densities for identifying edges of the figure are generated in the second position before the left edge of the figure and in the second position after the right edge of the figure.