1. An image processing apparatus detecting a plurality of joint positions between input images, comprising: circuitry configured to: generate target images to be searched in a second input image based on a first input image, the first input image and the second input image being among the input images; calculate a characteristic amount for each of the target images; and calculate a matching between a particular target image of interest among the target images, and a part of the second input image, using an evaluation method depending on the calculated characteristic amounts, wherein the characteristic amount is at least one of an edge amount, dispersion and standard deviation of the respective target image.