a novel image-based label system is proposed in this paper, we can convert the coordinate in image into Cartesian coordinate by using an image from a single CCD camera. This system could correspond arbitrary two points on the image convert to the actual distance no matter the digital camera is vertical to the measuring plane or not and the height of digital camera. Here designed a new structure for reach the goal of our proposed, first of all use four laser projector. Second, generate four laser spots on a measurement plane. Then, assume connect each two laser spot as parallel lines. Now we have simulated an automatically adjusts the resolution of the measurement ruler in the image. Because there's no capture angle constraint for the camera, it can use to measure horizontally such as: area of floor, or vertically such as: height of building.