someone suggested making a copy of the image and moving it 1 pixel up, another copy 1 pixel down, another 1 pixel to the right ect.

I see how it did it now. He took multiple copies of the img and layered them, then moved each layer by just one pixel in any direction. It creates a type of shadowing that makes the characters stand out. You just have to be careful not to adjust too much or you risk losing the shape of the character.