descriptive convenience a pixel coordinate of a pixel located in lower left corner of the 4 u00d7 4 pixel is defined as 0 0 and a pixel coordinate of a pixel located in upper right corner is defined as 3a 3b a represents a unit length in the direction of the x axis and b represents a unit length in the direction of the y axis where for a 1 b 1 the pixel code of each pixel coordinate in fig3 to 11 is represented in the following table 1 but it is not limited thereto where a b c d e f g h i j k l m n o and p are the original pixels and m u and l are the center point the top point and the left point of the pixels to be interpolated in order to improve the accuracy of the interpolation of the edge direction in the present invention the interpolation is to determine the edge direction of the 4 u00d7 4 pixel by using the above rules for calculating pixel values of the pixel to be interpolated of the center point m the top of the center point u and the left of the center point l in particular the 4 u00d7 4 special edges and the corresponding interpolated rule of the present invention are the different kinds of the special edges are divided in.