1. A method of determining a laundry load size in a laundry treating appliance comprising a rotatable drum at least partially defining a treating chamber for receiving laundry for treatment in accordance with a treating cycle of operation, an imaging device, and a controller having a processor, the method comprising: generating an image, with the imaging device, of a portion of the treating chamber having graduated markings; detecting, by the controller, at least one graduated marking in the generated image; and determining, by the controller, a load size based on the at least one graduated marking.