1. An image processing apparatus that can process a plurality of printer languages having respectively different raster operation (ROP) calculation rules, and receiving an input print data written in any one of the printer languages and performs rasterization into drawing data corresponding to the input print data, the image processing apparatus comprising: a converter that converts a target ROP code and ROP calculation rule of the input print data into another ROP code and ROP calculation rule that produce substantially same drawing data, and the converter performs the conversion when a process speed is increased if the another ROP code and ROP calculation rule are used.