1. An image recovery method for eliminating an effect of an environmental medium, comprising: receiving a captured image affected by the environmental medium; defining a respective local window with each pixel located at a center of the respective local window; and under an assumption that original radiance of all pixels within the respective local window are identical, performing a minimization estimation for each local window, to obtain a corresponding transmission of each pixel in the captured image; wherein the step of performing the minimization calculation for the each local window comprises: obtaining radiance of the captured image and the environmental medium, and a mathematical model of original radiance of each pixel without the effect of the environmental medium and the transmission; defining a cost function by assuming that original radiance of all pixels within the respective local window in the captured image are identical in the mathematical model; calculating the transmission and the original radiance that minimizes the cost function; and obtaining a transmission heuristic of the captured image, to guide the transmission by utilizing the transmission heuristic in the step of calculating the transmission and the original radiance that minimizes the cost function; wherein the step of utilizing the transmission heuristic to guide the transmission comprises: taking a greater value from an estimated result of performing the minimization estimation for each local window and a transmission value of each corresponding pixel in the transmission heuristic as the transmission of each corresponding pixel in the captured image.