1. An image processing method, comprising: detecting an edge from an image; extracting an edge line segment, being a straight line, from the edge; and deciding a strength of a sharpening process in a target pixel automatically based upon a length of the edge line segment existing near the target pixel of the sharpening process using a processor; performing sharpening of said image based upon the automatically decided strength of the sharpening process, wherein the deciding a strength of a sharpening process automatically decides the strength of the sharpening process based upon a length of a shortest edge line segment when a plurality of edge line segments exist adjacently.