A rendering command generator (11) acquires coordinate transformation information and a rendering region that converts and displays a reference image in a display image, and sets a coordinate transformation matrix in a register (21). A rendering block setting unit (22) sets the number of vertical and horizontal pixels of a rectangular region that divides and covers the rendering region in such a way that the region in which the rectangular region is subjected to coordinate transformation from a rendering region to a reference image by a coordinate transformation matrix conforms with the shape on the image of the image cache (15) from which the reference image is read out. A pixel generator (13) scans the rendering region by using the set rectangular region and generates pixel positions, and a coordinate transformation unit (14) reads out from external memory (20) image data on the pixel positions of the reference image corresponding to the pixels of the rendering region. The image cache (15) stores the image data read out from the external memory (20). A rendering processor (16) reads out image data from the image cache (15) and converts the image data to pixels of the rendering region.