1. An apparatus for processing an image, the apparatus comprising: a ghost information acquisition unit to acquire, from an overlapping region of a left image and a right image, ghost information based on an optimal threshold and a cost map; a tone correction map generator to generate a tone correction map, based on a global tone correction function generated using the ghost information, and based on a local tone correction level generated using local information of an optimal seam; and a bidirectional corrector to correct the left image and the right image using a final tone correction map generated by applying, to the tone correction map, a weighting based on the left image and a weighting based on the right image.