A video game apparatus functioning as a game image processing apparatus includes a CPU, and the CPU converts a resolution of a game image according to a game image processing program. A GPU draws an original game image on a frame buffer according to an instruction by the CPU. This is stored in a main memory as an original texture, and the original texture enlarged into double is drawn on the frame buffer. Next, when two texels adjacent to each other in a lower right direction and in an upper right direction have a same color, a semi-transparent texel in this color is drawn. Namely, a jaggy interpolation processing is applied.