1. A method for zooming images suitable for altering the size of a source image frame in both horizontal and vertical directions to generate a destination image frame, the method for zooming images comprising: multiplying a frequency of a horizontal sync signal by N to generate an operating clock signal for zooming in the source image frame and dividing the frequency of the horizontal sync signal by N to generate the operating clock signal for zooming out the source image frame, wherein the horizontal sync signal is synchronized with the source image frame, N is an integer and N is greater than 1; sampling the source image frame by using the operating clock signal and generating a sampled image frame; performing a horizontal zooming operation on the sampled image frame by using the operating clock signal, and generating a horizontal image frame; and performing a vertical zooming operation on the horizontal image frame by using the operating clock signal, and generating a vertical image frame.