An image forming apparatus and a method of controlling the image forming apparatus. When print data is printed, the remaining amount of toner of each of the CMYK colors is analyzed. When print data is printed, the apparatus analyzes an original color of the print data and analyzes respective remaining amounts of toner of a plurality of colors. If the remaining amount of toner of any of the plurality of colors is insufficient, the apparatus generates a plurality of corrected sample images having colors similar to the original color, the similar colors being obtained by combining colors of toner other than that of the insufficient remaining amount of toner, and prints a report including the generated plurality of corrected sample images. This allows the user to print their preferred colors even if the remaining amount of toner of any color is insufficient, thereby increasing convenience and economic efficiency.