Patent ID: 8805119

Claim:
An image rendering device, comprising one or more hardware processor to implement: a rendering region acquisition unit for acquiring information for specifying a rendering region, which is a region in which a reference image is converted and displayed, in a display image; a coordinate transformation information acquisition unit for acquiring information designating coordinate transformation from coordinates of the rendering region to coordinates of the reference image, for converting and displaying the reference image in the rendering region; a setting unit for setting vertical and horizontal pixel numbers in a rectangular region covering the rendering region such that a prescribed relationship is satisfied by a first region obtained by having the rectangular region undergo the coordinate transformation, and a second region positioned on the reference image and in response to image data recorded in an image cache that stores the reference image; a generation unit for generating one or more of the rectangular regions covering the rendering region with the vertical and horizontal pixel numbers set by the setting unit; a transformation unit for selecting the rectangular regions in order in a prescribed scanning direction, and computing pixel position within the reference image through the coordinate transformation from pixels selected in order in the scanning direction in the selected rectangular regions; an image acquisition unit for reading image data in the pixel position computed by the transformation unit from memory storing the reference image; the image cache for storing image data read from the memory; and a rendering unit for reading image data from the image cache and converting such into pixels in the rendering region; wherein the setting unit sets the vertical and horizontal pixel numbers in the rectangular region so that the rectangular region is small if the coordinate transformation magnification is large, and so that the rectangular region is large if said magnification is small.