1. An image processing apparatus comprising: an imaging unit configured to capture an image; an extraction unit configured to extract a feature amount in each image region of a plurality of objects from the captured image; a determination unit configured to determine, based on the extracted feature amount, a type of a feature amount used for discriminating each of the plurality of objects and a resolution of an image used for extracting a feature amount of the determined type; an imaging control unit configured to control the imaging unit to output an image at the determined resolution; and an extraction control unit configured to control the extraction unit to extract a feature amount of the determined type from the image output at the determined resolution from the imaging unit.