1. An image processing device comprising: predicted motion vector generation circuitry configured to generate a first predicted motion vector for a target block of a color image of a second viewpoint with respect to a color image of a first viewpoint different from the second viewpoint according to a depth information prediction standard, wherein the predicted motion vector generation circuitry is configured to calculate a disparity vector of the target block from a depth image of the second viewpoint and adopt the disparity vector as the first predicted motion vector for the target block, the disparity vector represents a disparity of the target block of the color image of the second viewpoint with respect to the color image of the first viewpoint, and the depth image of the second viewpoint comprises depth information related to a disparity of each pixel of the color image of the second viewpoint as a pixel value; the predicted motion vector generation circuitry configured to generate a second predicted motion vector for the target block of the color image of the second viewpoint with respect to the color image of the first viewpoint according to a median prediction standard, wherein the predicted motion vector generation circuitry is configured to calculate a median of disparity vectors of surrounding color blocks adjacent to the target block and adopt the median as the second predicted motion vector for the target block; and the predicted motion vector generation circuitry configured to select a final prediction motion vector for the target block of the color image of the second viewpoint with respect to the color image of the first viewpoint among the first predicted motion vector and the second predicted motion vector, based on a number of surrounding depth blocks in the depth image of the second viewpoint, a number of reference index matching blocks, and a variation of the disparity vectors of the surrounding color blocks adjacent to the target block of the color image of the second viewpoint.