1. An image based touch apparatus comprising: at least two region indicators, each of the at least two region indicators including a plurality of indication units and a touch sensor, wherein the indication units are configured to mark a touch surface; at least one image capturing apparatus capturing at least one image including the at least two region indicators; and a processing apparatus connected to the at least one image capturing apparatus to receive the at least one image, wherein the processing apparatus identifies position information of the indication units according to the indication units showed in the at least one image to define the touch surface according to a geometric structure formed by the indication units showed in the at least one image, when the touch sensor detects an operating object touches the touch surface, the indication units of the at least two region indicators generate a touch message, the touch message comprises visible light or invisible light, and the processing apparatus determines whether the touch message is showed in the at least one image and determines a position of the operating object on the touch surface according to the touch surface showed in the at least one image in response to the touch message being showed in the at least one image.