Put white dots on black background when it is an uniform dark area

around 40000 black dots and around 36000 white dots

This demo uses over 54000 black dots(saving 20000 dots) and around 3000 white dots.
Put white dots on chosen uniform dark area. It did work better for showing dark area. But the library for showing vector graphics I chosen only supports changing the whole background color not partially. So there might be a problem for showing vector graphics.

The white uniform area shows where the modified area is.