Aspects of this disclosure can provide a method that is applied to an image with a rectangular shape. The method can include dividing the image into a plurality of areas based on right angles of the image, and establishing a corresponding rectangular coordinate system for the right angle within each of the plurality of areas. Further, an intersection of a first axis and a second axis is taken as an origin of the rectangular coordinate system and a quadrant where the right angle is located is taken as a first quadrant of the corresponding rectangular coordinate system. The method can further include determining whether a pixel in the image is located in the first quadrant, and, if it is determined that the pixel is located in the first quadrant of the rectangular coordinate system, performing an operation on the pixel, otherwise, performing no operation on the pixel.