1. An image processing apparatus comprising a processor for executing a method comprising: an acquisition step of acquiring a frame image; an identification step of identifying a single minimum pixel value, wherein the single minimum pixel value is a minimum value of a first minimum pixel value, a second minimum pixel value, and a third minimum pixel value, the first minimum pixel value being a minimum value of pixel values of a first color component of all pixels within a predetermined area including a pixel of interest in the frame image, the second minimum pixel value being a minimum value of pixel values of a second color component of all pixels within the predetermined area including the pixel of interest in the frame image, and the third minimum pixel value being a minimum value of pixel values of a third color component of all pixels within the predetermined area including the pixel of interest in the frame image; a replacing step of replacing pixel values of the first, second, and third color components of the pixel of interest in the frame image with the single minimum pixel value identified in said identification step such that respective first, second, and third pixel values of the first, second, and third color components of the pixel of interest are equal; a low-pass filtering step of applying a low-pass filter processing to a preprocessed image, wherein the preprocessed image is generated based on replacing the pixel values in the replacing step; and an output step of outputting a first subframe image based on a result of the low-pass filter processing for the preprocessed image and of outputting a second subframe image based on a difference between the frame image acquired in the acquisition step and the first subframe, wherein the first and second subframes are output alternately in the output step.