Wheneven the mouse is over the large, white drawing area on the left, a 19-by-19 block of pixels is extracted from the drawing, and a magnified copy is shown in the area on the bottom right. Each pixel from the original image is shown as a square that is 8 pixels on a side. Results can be different in different browsers.
(Note for touch screen users: You have to touch the display area to see the magnified pixels.)
You can draw on the drawing area by dragging your mouse on it. The radio buttons on the right let you draw black lines, red rectangles, and blue circles. Selecting "None" means that dragging the mouse will only display unmagnified pixels.
The "Clear" button fills the drawing area with white. The "Reset" button restores the original image.
Things to try: Point your mouse at the text in the original image, and note how the text is anitaliased. Check out the difference between the two lines in the original image. Draw a line that is almost vertical or almost horizontal, and look at at how the line is antialiased. Look at the boundary of a circle. Draw a red rectangle then a blue circle that intersects it, and look at how the blue blends with the red along the boundary between them.
To close this help screen, click the "Close" button at the top left.