1. A projector device, comprising: an image projecting unit for projecting an image; and a control unit for acquiring brightness information of regions included in a projection surface on which the image is projectable by the image projecting unit, and determining a projection region on which the image is to be projected by the image projecting unit based on the brightness information of the regions, wherein the projection region is a low-brightness region, among the regions, whose brightness is lower than that of another region.