A source image with an input vertical resolution and an input horizontal resolution is received using an input clock signal. An intermediate image with an output vertical resolution and the input horizontal resolution is generated using an intermediate clock signal by scaling the source image. An output image with the output vertical resolution and an output horizontal resolution is generated using an output clock signal by scaling the intermediate image. The frequency of the intermediate clock signal is equal to the frequency of the output clock signal multiplied by the ratio of the input horizontal resolution to the output horizontal resolution.