A method for resizing an image is disclosed. In a preferred embodiment, the method projects the image onto a lateral surface of a three-dimensional cylinder to transform the image into a three-dimensional image. Then, the method applies perspective projection (with a chosen viewpoint) to transform the three-dimensional image back to a two-dimensional image, based on which a final resized image is generated. By carefully choosing the diameter of the three-dimensional cylinder and the coordinate of the viewpoint, a rectangular shaped image may be resized into a square-shaped image.