Image processing apparatus, image processing method, and storage medium

An image processing method comprising:

• performing first noise reduction processing on a plurality of radiation images corresponding to mutually-different radiation energies;
• generating a decomposition image by energy subtraction processing using the plurality of radiation images obtained by performing the first noise reduction processing;
• and
• performing second noise reduction processing on the decomposition image, the second noise reduction processing using a filter that differs from a filter used in the first noise reduction processing in at least one of size and type.

An image processing method comprising:

• generating a decomposition image by energy subtraction processing using a plurality of radiation images corresponding to mutually-different radiation energies;
• generating a pseudo decomposition image using a radiation image to which the energy subtraction processing is not applied and a predetermined constraint;
• and
• determining, using the decomposition image, a combining ratio pertaining to combining of the decomposition image and the pseudo decomposition image.