1. A method comprising: receiving a representation of an image over a computer network; in automated operations performed using one or more processors configured to perform the automated operations: extracting encoded alpha channel data from the representation of the image; extracting color data from the representation of the image, the color data being separate from the alpha channel data; identifying at least one common type pixel run represented in the encoded alpha channel data; identifying at least one lookup type pixel run in the encoded alpha channel data; rendering the image by: applying a common alpha channel value to each of a first plurality of pixels in the color data correlating to the at least one common type pixel run; and applying a plurality of selected alpha channel values to each of a second plurality of pixels in the color data correlating to the at least one lookup type pixel run, the selected alpha channel values selected from lookup data extracted from the representation of the image; and displaying the color data with the applied alpha channel values on a graphical display.