1. A method of rendering an image, the method comprising: determining a transparency of a destination pixel at a plurality of samples in the destination pixel; determining a transparency of a source pixel at a plurality of samples in the source pixel, the destination pixel being in front of the source pixel; and determining a new pre-multiplied color of the destination pixel in response to the transparencies of the destination pixel, the transparencies of the source pixel, a color of the source pixel and a pre-multiplied color of the destination pixel.