Provided are an image processing apparatus, a control method, and a control program for more accurately removing the background pattern from the image including the background pattern. An image processing apparatus includes an acquisition module to acquire an input image, a multi-valued image generating module to generate a multi-valued image from the input image, a binary image generating module to generate a binary image acquired by binarizing the input image, a detection module to detect a thin line having a width equal to or less than a predetermined number of pixels from the multi-valued image, a background pattern removal image generating module to generate a background pattern removal image in which the thin line is removed from the binary image, based on the thin line detected from the multi-valued image, and an output module to output the background pattern removal image or information generated using the background pattern removal image.