1. An image processing apparatus, comprising: a full feature point detection section for detecting, as a full feature point, a point whose pixel value changes significantly in any direction; a semi feature point detection section for detecting, as a semi feature point, a point whose pixel value of the image hardly changes in a certain direction but changes significantly in other directions; a first tracking section for tracking the full feature point between a first image and a second image; a second tracking section for tracking the semi feature point; and an alignment section for aligning the inputted image based on a tracking result made by the first tracking section and the second tracking section.