In an image forming apparatus (10), a feature extracted image forming unit (11) includes a line-drawing unit (11A). The line-drawing unit (11A) draws in an image to be processed, for each of a plurality of line-draw groups, a line that passes all the key points included in each of the line-draw groups and has at least one end that is extended to an end of the image to be processed, thereby forming a texture map. Each of the line-draw groups includes at least two key points included in the plurality of predetermined key points.