An image processing method implemented on a computer, the method comprising: obtaining a depth image of a protuberant object, wherein the depth image includes a region of interest; for each pixel of the region of interest of the depth image selecting a plurality of test points placed on a circle of radius r(d c) around a selected pixel in the depth image as a center point of the circle, wherein the selected pixel and pixels corresponding to the test points have a respective depth value and wherein the radius of the circle is determined by the depth value of the selected pixel, wherein the radius is inversely proportional to the depth value of the center point d c; calculating a protuberance value f c of the center point by comparing the depth value of the center point and the depth value of each of the selected test points; and determining one or more salient points of the protuberant object by using the protuberance value f c of each pixel in the depth image, wherein each pixel of the region of interest in the depth image is mapped into a protuberant saliency map with a protuberance value f c; wherein calculating the protuberance value f c comprises: counting the number of positive comparison results associated with the selected test points, wherein a positive comparison result is generated if the depth value of one test point is larger than the depth value of the center point, wherein the larger the number of positive comparison results is the larger the protuberance value of the center point is. obtaining a depth image of a protuberant object, wherein the depth image includes a region of interest; for each pixel of the region of interest of the depth image selecting a plurality of test points placed on a circle of radius r(d c) around a selected pixel in the depth image as a center point of the circle, wherein the selected pixel and pixels corresponding to the test points have a respective depth value and wherein the radius of the circle is determined by the depth value of the selected pixel, wherein the radius is inversely proportional to the depth value of the center point d c; calculating a protuberance value f c of the center point by comparing the depth value of the center point and the depth value of each of the selected test points; and determining one or more salient points of the protuberant object by using the protuberance value f c of each pixel in the depth image, wherein each pixel of the region of interest in the depth image is mapped into a protuberant saliency map with a protuberance value f c; wherein calculating the protuberance value f c comprises: counting the number of positive comparison results associated with the selected test points, wherein a positive comparison result is generated if the depth value of one test point is larger than the depth value of the center point, wherein the larger the number of positive comparison results is the larger the protuberance value of the center point is. counting the number of positive comparison results associated with the selected test points, wherein a positive comparison result is generated if the depth value of one test point is larger than the depth value of the center point, wherein the larger the number of positive comparison results is the larger the protuberance value of the center point is.