1. An image processing apparatus comprising: circuitry that compares a first image and a second image, determines a plurality of corresponding points between the first image and the second image, forms groups from the plurality of corresponding points, acquires a coordinate transformation coefficient for each of the groups, and generates a synthesis image using a plurality of the coordinate transformation coefficients, wherein, when acquiring the coordinate transformation coefficient, a first group containing a first part of the plurality of corresponding points and a second group containing a second part of the plurality of corresponding points which is different from the first part are generated, and a first coordinate transformation coefficient corresponding to the first group and a second coordinate transformation coefficient corresponding to the second group are acquired, wherein, when generating the synthesis image, the synthesis image is generated by using the first coordinate transformation coefficient and the second coordinate transformation coefficient.