Patent ID: 8907949

Claim:
An image display apparatus comprising: a three-dimensional image obtainment unit that obtains a three-dimensional image representing an observation target; an image generation unit that generates a projection image from the three-dimensional image by projecting the observation target in a predetermined projection direction; a display control unit that displays the generated projection image on a display screen of a display device; a movement input reception unit that receives user movement input for moving the display position of the projection image on the display screen to thereby allow the user to manually move the display position of the projection image for placing the projection image at a vicinity of a center on the display screen; a candidate region determination unit that sets, as a set region, a region extending in the predetermined projection direction from a central part of the display screen, and that determines, as a rotation center candidate region, at least a part of an overlapped region between the set region and the observation target, wherein the overlapped region is determined when an overlapped region between the set region and the observation target, which projects the projection image at the display position moved by receiving the movement input from the movement input reception unit, is present; and a rotation center determination unit that determines a center of rotation in the determined rotation center candidate region or in the vicinity thereof, the center of rotation being determined, within the rotation center candidate region, after the candidate region determination unit establishes the presence of the overlapped region, wherein i) the movement input reception unit receiving the user movement input moving the display position of the projection image on the display screen and ii) the candidate region determination unit establishing the presence of the overlapped region and then setting the rotation center candidate region are performed repeatedly, and after the candidate region determination unit determines the rotation center candidate region, the rotation center determination unit determines the center of rotation.