A distance measurement method is provided. The distance measurement method includes obtaining an image of a target device, the image of the target device including a target object of a first color and a background object of a second color, the first color being different from the second color; processing the image of the target device to obtain a processed image, the processed image including a processed target object of a third color and a processed background object of a fourth color; detecting a contour of the processed target object of the third color; calculating an area encircled by the contour; and calculating a distance between a camera and the target device upon determination of the area encircled by the contour.