1. A display device comprising: a display unit having a plurality of block regions each formed with pixels of three or more channels, wherein each pixel is one of: a red pixel, a green pixel, or a blue pixel, and each of the channels being associated with a respective parallax image; a separating unit configured to separate an image displayed on pixels of the respective channels in the block regions, wherein each one of the plurality of block regions includes a viewing opening; an allocation control unit configured to allocate one of parallax images to pixels of the respective channels in the block regions in accordance with a viewpoint position of a user viewing the display unit, one of the parallax images of a same viewpoint being displayed in a first region that is formed with pixels adjacent to one another in the block regions and is also formed with pixels of two or more different channels in a direction of parallax, another one of the parallax images having a parallax with respect to the one of the parallax images being displayed in a second region different from the first region in the block regions; a viewed position calculating unit configured to determine a viewed position of a viewed pixel to be viewed by a user in each of the block regions based on the viewpoint position; a boundary position calculating unit configured to calculate a boundary position that is a position of a block region in which the viewed position is substantially a center of the viewed pixel, and allocates the same one of the parallax images to pixels of the same channel in each of the block regions located between the boundary position and another boundary position closest to the boundary position; and a generating unit configured to generate a combined image by combining the parallax images in accordance with the allocation performed by the allocation control unit, wherein each of the block regions comprise at least one pair of adjacent channels that are associated with a same parallax image, and wherein the display unit, the separating unit, the allocation control unit, the viewed position calculating unit, the boundary position calculating unit and the generating unit are each implemented via at least one processor.