An image area detector detects a high-luminance image area having a luminance value equal to or higher than a predetermined value, having a size equal to or larger than a predetermined size, and including two or more high-luminance subject images disposed adjacent to or overlapping with each other, from an input image frame. The enlargement controller controls the detected high-luminance image area to be enlarged and displayed. If any instruction to designate a subarea within a rectangular border surrounding the enlarged high-luminance image area is provided from the user, the position coordinate setter converts the coordinates of the subarea into the coordinates before the enlargement, and stores the converted coordinates into the memory as the coordinates of the LED serving as a light source that transmits information.