Patent ID: 7697016

Claim:
An image display device having a function of rotating a display image around a center point of rotation, the image display device, comprising: a comparison unit for making a comparison (i) between a vertical length of an outer edge of a display region in which the display image is displayed and a vertical length of the display image and (ii) between a horizontal length of the outer edge of the display region in which the display image is displayed and a horizontal length of the display image; a storage unit in which the display image is stored; a first center-of-rotation determination unit for determining, as the center point of rotation, a center of the display image displayed in the display region and stored in the storage unit; a second center-of-rotation determination unit for determining, as the center point of rotation, a point of intersection between (i) a line extending perpendicularly from a middle point of a vertical side of the outer edge of the display region and (ii) a line extending perpendicularly from a middle point of a horizontal side of the outer edge of the display region; a third center-of-rotation determination unit for selecting a shorter one of the vertical lengths and a shorter one of the horizontal lengths in accordance with a result of the comparison made by the comparison unit (a) between the respective vertical lengths of the outer edge of the display region in which the display image is displayed and the display image stored in the storage unit and (b) between the respective horizontal lengths of the outer edge of the display region in which the display image is displayed and the display image stored in the storage unit, and then determining, as the center point of rotation, a point of intersection between (1) a line extending perpendicularly from a given point of one of the two sides thus selected and (2) a line extending perpendicularly from a given point of the other one of the two sides thus selected; and a selection unit for selecting any one of the first to third center-of-rotation determination units.