1. An image processing apparatus comprising: an image obtaining unit that obtains a plurality of low-resolution images acquired in time series; a movement detecting unit that detects a movement between the plurality of low-resolution images; a position alignment unit that performs position alignment of the plurality of low-resolution images on the basis of the movement and that performs pixel arrangement of the plurality of low-resolution images in an image space having a higher resolution than the low-resolution images, to generate a high-resolution image; a correlation calculating unit that calculates, for each partial area in the high-resolution image, correlation information indicating the degree of correlation between corresponding areas of the low-resolution images, the areas corresponding to this partial area; an image-to-be-composited generating unit that generates an image to be composited having a lower resolution than the high-resolution image on the basis of the plurality of low-resolution images or the high-resolution image; a compositing-ratio calculating unit that calculates, for each partial area, a compositing ratio between the high-resolution image and the image to be composited, on the basis of the correlation information; and an image compositing unit that generates a composite image of the high-resolution image and the image to be composited, according to the compositing ratio, wherein the compositing-ratio calculating unit calculates, for each partial area, the compositing ratio such that the proportion of the high-resolution image becomes smaller as the correlation of the area decreases, and the proportion of the high-resolution image becomes larger as the correlation of the area increases.