An image processing method for extracting a point positioned at a boundary between regions having different colors, from a color image constituted by pixels, the color of each pixel being expressed as three independent color parameters each defining a color parameter value, the method comprising: a step A of setting a first processing object region having a predetermined size and centering the first processing object region around a pixel of the color image to be processed; a step B (ST5 to ST8) of finding the magnitude of color change in each of X and Y directions crossing perpendicularly in the pixel in the center of the first processing object region using the color parameter values of pixels in the first processing object region and determining the pixel to be an edge point pixel when the sum of the magnitude of the color change in each of the X and Y directions found exceeds a predetermined threshold value; a step C (ST13 to ST16) of determining, In a second processing object region centered around the edge point pixel, that a vector showing the direction of a color parameter value change corresponds to which quadrant in a coordinate system defined by the X and Y directions, based on color parameter values of at least one color parameter of the pixels in the second processing object region; and a step D (ST17 to ST18) of specifying a direction of the change in color in the edge point pixel in the second processing object region, using the determination result at the step C and the magnitude of the color change in the X and Y directions found at the step B; wherein at the step C (ST13 to ST16), when the coordinate system defined by the two orthogonal X and Y directions is coordinated to the pixel arrangement in the second processing object region, the difference in the color parameter value between two points such as two points on a line parallel to any line among line group connecting the first quadrant and the third quadrant in the coordinate system, and two points on a line parallel to any line among line group connecting the second quadrant and the fourth quadrant in the coordinate system are extracted, and the quadrant corresponding to the vector connecting the two points having a greater difference value is determined as the quadrant corresponding to the vector showing the direction of the change of the color parameter. a step A of setting a first processing object region having a predetermined size and centering the first processing object region around a pixel of the color image to be processed; a step B (ST5 to ST8) of finding the magnitude of color change in each of X and Y directions crossing perpendicularly in the pixel in the center of the first processing object region using the color parameter values of pixels in the first processing object region and determining the pixel to be an edge point pixel when the sum of the magnitude of the color change in each of the X and Y directions found exceeds a predetermined threshold value; a step C (ST13 to ST16) of determining, In a second processing object region centered around the edge point pixel, that a vector showing the direction of a color parameter value change corresponds to which quadrant in a coordinate system defined by the X and Y directions, based on color parameter values of at least one color parameter of the pixels in the second processing object region; and a step D (ST17 to ST18) of specifying a direction of the change in color in the edge point pixel in the second processing object region, using the determination result at the step C and the magnitude of the color change in the X and Y directions found at the step B; wherein at the step C (ST13 to ST16), when the coordinate system defined by the two orthogonal X and Y directions is coordinated to the pixel arrangement in the second processing object region, the difference in the color parameter value between two points such as two points on a line parallel to any line among line group connecting the first quadrant and the third quadrant in the coordinate system, and two points on a line parallel to any line among line group connecting the second quadrant and the fourth quadrant in the coordinate system are extracted, and the quadrant corresponding to the vector connecting the two points having a greater difference value is determined as the quadrant corresponding to the vector showing the direction of the change of the color parameter.