1. An image processing apparatus for performing rendering processing, the image processing apparatus comprising: an input unit configured to input an object expressed by line information connecting a first point and a second point; a classification unit configured to classify a graphic type of the object based on the line information expressing the object; and a processing unit configured to switch a procedure generating edge information for rendering processing according to the graphic type classified by the classification unit, the rendering processing generating a bitmap from the line information, wherein the processing unit is configured to perform scan-line edge detection to generate the edge information without regard to the graphic type classified by the classification unit when the input unit inputs objects of more than a predetermined number.