1. An image transmission method for a mobile communication terminal, the method comprising: capturing, via a camera on the mobile terminal, a picture image of a user of the mobile terminal to be transmitted to another terminal during a video call; receiving, via an input unit, characters to be synthesized within the picture image; preparing, via a controller on the mobile terminal, a character image composed of a character part including the input characters and a background part; synthesizing, by the controller, the character image and the picture image to produce a synthesized image; and transmitting, via a wireless communication unit, the synthesized image to said another terminal during the video call, wherein the background part is in a single color, wherein the synthesizing step includes filling the background part of the character image with the picture image such that the character part of the character image is inserted into the picture image, and wherein the synthesizing step includes matching the character image with the picture image on a one-to-one basis for each pixel and replacing only each pixel of the background part with a pixel of the picture image corresponding to the pixel.