1. A method for processing information, the method comprising: calculating at least one difference value between a pixel value of a target pixel in an input image obtained by capturing a document image and a pixel value of a corresponding pixel in a shade component image at coordinates identical to those of the target pixel, the shade component image representing shade components of the input image, the shade components depending on an image capture environment; and correcting the pixel value of the target pixel in the input image based on a correction rate to correct a shade component in the target pixel, the correction rate depending on at least one difference value associated with the target pixel in the input image.