1. An image processor for use in drawing an image to a memory having a two-dimensional matrix of pixel drawing regions, each of the pixel drawing regions representing a single pixel in the image, said image processor comprising: a plurality of relative orientation detection filters each representing a distinguishing feature of a relative orientation of an edge segment to be drawn to the memory; drawing means for drawing the image to the memory or a buffer having the same structure as the memory; detection means for automatically detecting a connected sequence of pixel drawing regions making up an edge in the image drawn by said drawing means by applying an edge extraction filter, and detecting the relative orientation of the connected sequence of pixel drawing regions by means of selecting out a predetermined number of relative orientation detection filters each representing a distinguishing feature that is closer to the distinguishing feature of the connected sequence of pixel drawing regions in question, and performing interpolation with the relative orientations specified by the selected relative orientation detection filters; and smoothing means for smoothing a pixel value of each pixel in the connected sequence of pixel drawing regions on the edge using smoothing coefficients, the smoothing coefficients being either computed depending on the relative orientation detected by said detection means or obtained from outside, wherein each of said plurality of relative orientation detection filters is a two-dimensional matrix of predetermined orientation coefficients, the orientation coefficients including zero orientation coefficients each having a value of zero and non-zero orientation coefficients each having a value other than zero, the non-zero orientation coefficients being aligned relative to each other in a predetermined direction, said detection means performing convolution of all orientation coefficients contained in said relative orientation detection filters, with each pixel value of the connected sequence of pixel drawing regions making up the edge, selecting out a predetermined number of relative orientation detection filters for which their respective convolution results in a single direction exceed a predetermined threshold value and yield the largest result, the second largest result, and the third largest result, respectively, as the relative orientation filters having their respective distinguishing features that are closer to the distinguishing feature in the subject direction, and distributing, using interpolation, the relative orientations specified by the selected relative orientation detection filters, thereby determining one relative orientation.