1. An image forming apparatus capable of generating image data of print data containing a drawing object to be reused within a job, the image forming apparatus comprising: a processor coupled to a memory; an object parallel processing unit configured to execute object raster image processor (RIP) processing in parallel per drawing object unit; a page parallel processing unit configured to execute page RIP processing in parallel per page unit; a cache unit configured to generate receive generated drawing object data that was generated based on numeric quantity of the drawing object and cache the generated drawing object data based on the drawing object; an obtaining unit configured to obtain a ratio of a cached drawing object based on cached drawing object, generated based on numeric quantity of the drawing object, and the drawing object which is used in a page; and a determination unit configured to determine whether the ratio of the drawing object which is used in a page and cached drawing object data exceeds a threshold, wherein, when the determination unit determines that the ratio does not exceed the threshold, the object parallel processing unit executes the object RIP processing, and, after the object parallel processing unit executes the object RIP processing, the determination unit determines whether the ratio exceeds the threshold, wherein, when the determination unit determines that the ratio exceeds the threshold, the page parallel processing unit executes the page RIP processing, and wherein at least the object parallel processing unit, the page parallel processing unit, the cache unit, the obtaining unit, and the determination unit are implemented by the processor in the image forming apparatus.