Question

I need your advise. It’s about this app:

LEDit Free

EDIT: The referenced app displays text in the way a lighted board would, as a series of illuminated dots.

Basically you can insert your text and it will be scrolled through the screen. You can try it youself, there’s a light version

But how did they manage to put the individual text exactly on the image with it’s circles? I think it is very labour-intensive, isn’t it?

Answer 1

When we used to do this with real LED displays, we just used bitmaps. So for example, the character H and A could be defined (in its simplest form) as arrays of booleans:

bool[] H = { 1,0,0,0,0,1,   bool[] A = { 0,0,1,1,0,0,
             1,0,0,0,0,1,                0,1,0,0,1,0,
             1,1,1,1,1,1,                0,1,1,1,1,0,
             1,0,0,0,0,1,                1,0,0,0,0,1,
             1,0,0,0,0,1 }               1,0,0,0,0,1 }

Then for each character in the text it finds the right bitmap in the table and turns on the right LEDs, or in this case it switches the right images.