Most display screens have hundreds of thousands of pixels. Each pixel has to be set to the right colour (most display screens are capable of 16 million colours in each pixel). To make a clear picture, the screen might need to make millions of calculations. Any group of pixels that change to the same colour can be changed with one calculation, making the calculations much smaller. For example, if the picture to display was just a white screen, the screens processor would only calculate the colour once and use the same calculation for the whole screen. Changing one pixel at a time would take many more calculations. If the same picture was shown many times on the screen, the processor would calculate the picture once and then repeat it in whatever position and in different sizes, if needed. The processor can make very complicated calculations, but in the end it does less work. This is called rendering technology. Rendering technology in the most modern displays is like making a .