1. An image processing apparatus comprising: an estimation unit configured to estimate a scattered-ray component contained in a radiation image acquired by irradiating an object with a radiation, wherein the scattered-ray component originates from a scattered ray which is a radiation scattered in the object; a noise reduction unit configured to reduce a noise component included in the radiation image in accordance with first noise information obtained from the radiation image and second noise information obtained from a scattered-ray reduction image obtained by reducing the scattered-ray component from the radiation image; and an output unit configured to output a correction image obtained by reducing the scattered-ray component and the noise component in the radiation image.