1. An image forming method of a print controlling apparatus, the method comprising: extracting two or more graphical primitives included in print data; forming an image by arranging the two 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 a portion of the graphical primitives, which corresponds to the sketch image, with the sketch image such that draft-printing is performed using the modified print data.