1. A method for processing an image on a portable terminal equipped with a dual camera, the method comprising: selecting an image synthesis mode; performing a simultaneous or a sequential photographing of a front camera and a rear camera; obtaining a first image and a second image through the front camera and the rear camera; detecting an object image from one of the first image and the second image; determining whether at least one of the obtained first image or second image is identical to a stored information and extracting a first effect which is previously mapped to the stored information when the at least one of the obtained first image or second image is identical to the stored information as a result of the determination; generating a synthesized image by synthesizing the object image to the other of the first image and the second image in which the object image was not detected and applying the first effect to the synthesized image; and displaying the synthesized image to which the first effect is applied, wherein the generating of the synthesized image comprises detecting at least one of a photographing based position information or a photographing based time information, extracting a second effect previously mapped to the at least one of information of the detected photographing based position or the photographing based time, and displaying the second effect to the synthesized image, and wherein the second effect comprises information related to at least one of a schedule or a location which is mapped to the at least one of the detected photographing based position information or the photographing based time information.