1. An image processing apparatus comprising: attribute information generation means for generating attribute information indicating an attribute of an image in correspondence with a command that represents the image, where the attribute information includes a first bit indicating whether or not an object to be rendered in accordance with the command has a text attribute, a second bit indicating whether or not the object to be rendered has a vector attribute, and a third bit indicating whether or not the object to be rendered has a chromatic attribute; bitmap data generation means for generating bitmap image data by rendering the command; and image processing means for performing an image process of the bitmap image data in accordance with the attribute information, wherein attribute information at an overlapping position of first and second images is generated by, in accordance with the command for the first and second images, executing a logical operation of each bit of the attribute information of the first image and corresponding bits of the attribute information of the second image to determine a value of the first to third bits of the attribute information of the overlapping position, and wherein bitmap image data at the overlapping position of the first and second images is generated by synthesizing, in accordance with the command for the first and second images, the first image and the second image.