1. An image processing apparatus including a reading sensor configured to read an original image, the image processing apparatus comprising: an image data acquiring unit configured to acquire image data of a plurality of frames of images in which positions read by the reading sensor are shifted by less than one pixel in a main scanning direction and/or a sub-scanning direction; a high-resolution converting unit configured to perform interpolation by using the plurality of frames of image data acquired by the image data acquiring unit to obtain image data having resolution higher than resolution of the reading sensor; an image region information generating unit configured to generate image region information including image region bits from the image data acquired by the reading sensor; an image region information converting unit configured to convert the image region information generated by the image region information generating unit into a format capable of being input to the high-resolution converting unit; an image region information high-resolution converting unit configured to perform a high-resolution conversion on the image region information whose format has been converted by the image region information converting unit, by using the high-resolution converting unit; and an image region information regenerating unit configured to regenerate the image region information, which has been converted to have the high resolution by the image region information high-resolution converting unit, as image region information having the same resolution as that of the image data converted to have the high resolution by the high-resolution converting unit.