1. An image forming method of a print controlling apparatus, the method comprising: extracting one or more graphical primitives from print data; forming an image by arranging the one or more graphical primitives according to a determination of whether the extracted graphical primitives are disposed close to each other; converting the formed image into a sketch image; and modifying the print data by replacing the sketch image and a portion of the graphical primitives constituting the sketch image such that draft-printing is performed using the modified print data.