Image rendering device, image rendering method, and recording medium

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 rectangular regions covering the rendering region;
• a generation unit for generating one or more of the rectangular regions covering the rendering region with the rectangular regions 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 when a smaller angle formed by the direction of the horizontal direction of the rendering region after coordinate transformation and the horizontal direction of a region corresponding to image data recorded in an image cache in which the reference image is stored and positioned on the reference image exceeds 45 degrees, the transformation unit switches a primary scanning direction and an auxiliary scanning direction of the primary scanning direction, selects in order rectangular regions covering the rendering region, and scans the selected rectangular region to select pixels.

An image rendering method 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;
• 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;
• setting the size of rectangular regions such that a prescribed relationship is satisfied by a first region obtained by having the rectangular regions 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;
• generating one or more rectangular regions covering the rendering region with the vertical and horizontal pixel numbers set by the set size;
• 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;
• reading image data in the computed pixel position from memory storing the reference image;
• storing image data read from the memory;
• and
• reading image data from the image cache and converting such into pixels in the rendering region;
• wherein the setting step 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.

An image rendering method 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;
• 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;
• setting rectangular regions for covering the rendering region;
• generating one or more of the rectangular regions covering the rendering region with the set rectangular regions;
• 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;
• reading image data in the pixel position computed by the coordinate transformation from memory storing the reference image;
• storing image data read from the memory;
• reading image data from the image cache and converting such into pixels in the rendering region;
• and
• when a smaller angle formed by the direction of the horizontal direction of the rendering region after coordinate transformation and the horizontal direction of a region corresponding to image data recorded in an image cache in which the reference image is stored and positioned on the reference image exceeds 45 degrees, the transformation switches a primary scanning direction and an auxiliary scanning direction of the primary scanning direction, selects in order rectangular regions covering the rendering region, and scans the selected rectangular region to select pixels.

A non-transitory computer-readable recording medium on which is recorded a program that causes a computer to execute:

• a process 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 process 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 process for setting the size of rectangular regions such that a prescribed relationship is satisfied by a first region obtained by having the rectangular regions 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 process for generating one or more of the rectangular regions covering the rendering region with the set size;
• a process 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;
• a process for reading image data in the computed pixel position from memory storing the reference image;
• a process for storing image data read from the memory;
• and
• a process for reading image data from the image cache and converting such into pixels in the rendering region;
• wherein the setting step 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.

A non-transitory computer-readable recording medium on which is recorded a program that causes a computer to execute:

• a process 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 process 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 process for setting rectangular regions for covering the rendering region;
• a process for generating one or more of the rectangular regions covering the rendering region with the set rectangular regions;
• a process 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;
• a process for reading image data in the pixel position computed by the coordinate transformation from memory storing the reference image;
• a process for storing image data read from the memory;
• a process for reading image data from the image cache and converting such into pixels in the rendering region;
• and
• a process for, when a smaller angle formed by the direction of the horizontal direction of the rendering region after coordinate transformation and the horizontal direction of a region corresponding to image data recorded in an image cache in which the reference image is stored and positioned on the reference image exceeds 45 degrees, the transformation switches a primary scanning direction and an auxiliary scanning direction of the primary scanning direction, selects in order rectangular regions covering the rendering region, and scans the selected rectangular region to select pixels.