1. An image processing apparatus, comprising: an image receiver which acquires a first image and a second image; a feature point extractor which extracts a plurality of feature points from the first image; a corresponding point detector which detects a plurality of corresponding points by tracking, in the second image, a plurality of points in the second image respectively corresponding to the plurality of feature points extracted from the first image; an image transformation parameter calculator which calculates an image transformation parameter for matching the first image and the second image with each other among the detected plurality of corresponding points; an image transformer which transforms the second image using the calculated image transformation parameter and acquires the transformed image as a third image; and a feature point existing region detector which determines whether or not the feature point extracted from the first image is positioned in an invalid image region at a circumference of the image, the invalid image region which is a region of invalid pixels being generated by execution of a predetermined filtering process on the first image, wherein the corresponding point detector, when it is determined that the feature point extracted from the first image is positioned in the invalid image region, tracks the determined feature point using the first image and the third image.