1. An image processing apparatus, comprising: a storage unit configured to associate and store a signal value pattern of a high-resolution image and a signal value pattern of a low-resolution image that has been converted to a low resolution from the high-resolution image; an acquisition unit configured to, according to a result of matching a signal value pattern of an inputted image with the signal value pattern of the low-resolution image, acquire the signal value pattern of the high-resolution image that is associated with the signal value pattern of the low-resolution image from the storage unit; and a setting unit configured to use the signal value pattern acquired by the acquisition unit, to set signal values of an image after high-resolution conversion of the inputted image.