1. A method executed by a computer system to detect an edge of an object with a Canny operator, the method comprising: executing, by the computer system, a Gaussian filter to smooth an image of the object so that noise of the image is removed; calculating, by the computer system, a gradient strength of pixels of the image; applying, by the computer system and to the image, non-maximum suppression to avoid spurious responses to edge detection; dividing, by the computer system, the image into multiple partitions based on a brightness distribution of the pixels in the image; calculating, by the computer system and for each of the multiple partitions, a set of dynamic threshold values of T_high and T_low based on the brightness distribution of the pixels within each of the multiple partitions; obtaining, by the computer system and for each of the multiple partitions, a first image by setting to 0 the gradient strength of each pixel that is less than the T_high; obtaining, by the computer system and for each of the multiple partitions, a second image by setting to 0 the gradient strength of each pixel that is less than T_Iow; and detecting, by the computer system, the edge of the object by superimposing the first image and the second image.