generate, by performing binarization processing for a document image obtained by reading a document, a first binary image including first pixels representing a color darker than a reference level in the document image and second pixels representing a color paler than the reference level;

generate, based on the generated first binary image, a removal candidate image which represents a background object whose color is different from a color of a character object in the document image; and

generate a second binary image in which a background object that overlaps the character object in the document image is removed, by performing a changing processing to change one of the first pixels included in the first binary image corresponding to a unit area in which the number of pixels having the color of the character object within a corresponding area of the document image is more than a threshold value among the unit areas representing each background object in the removal candidate image to one of the second pixels.