This tool was developed from "Chris" over at LaptopShowcase.co.uk
Here's the description from him:
This is a program for testing LCD screens for dead pixels.
Before trying to grasp the meaning of a dead pixel, first you need to understand the technology behind LCD displays. An LCD display is essentially made up of pixels. Each pixel is made up of red, blue and green valves. The valves in each colour either block or pass the light source. By manipulating the amount of light passed through, each pixel displays a distinctive colour on screen. Pixels consisting of these valves are what make up the image that is ultimately displayed on the screen. A typical monitor has millions of pixels. A dead pixel refers to a pixel with a defect in its ability to display the correct colour output. It may look like a tiny black spot on your screen, or any other colour that does not correspond to what the actual image should look like.
A typical 17 inch monitor contains up to 4 million pixels. Even a tiny dust particle on one of the pixels during the manufacturing process can create a dead pixel. Or a slight bump during shipping can break one of the highly sensitive pixels.
If you've scoured every inch of your screen but can't find a single dead pixel, you are in luck. Because of the complexity of the design, it is generally regarded dead pixels appearing in some products are inevitable. If you need to absolutely make sure whether you have purchased a defective display, you can use this program. It simply paints your entire screen with one of the colours that make up a pixel to make the dead pixel more conspicuous to the naked eye. Run through the red, green and blue colours in turn and check for pixels that do not match.