An image processing method includes calculating a first feature-quantity that includes feature-quantities for indicating features of individual pixel values of pixels located in a first direction perpendicular to a first line segment out of line segments and feature-quantities for indicating features of individual pixel values of pixels located in a second direction opposite to the first direction with respect to the first line segment, and calculating, based on pixel values of pixels located for each predetermined distance in a third direction perpendicular to a second line segment out of the line segments and pixel values of pixels located for each of the predetermined distance in a fourth direction opposite to the third direction with respect to the second line segment, a second feature-quantity that includes feature-quantities for indicating individual features of the pixels located for each of the predetermined distance from the second line segment.