draw method
Implementation
@override
void draw(Canvas canvas, double space, double size, double radius) {
double progress = page - index;
double dropHeight = widget.dropHeight;
double rate = (0.5 - progress).abs() * 2;
double scale = widget.scale;
//lerp(begin, end, progress)
canvas.drawCircle(
new Offset(radius + ((page) * (size + space)),
radius - dropHeight * (1 - rate)),
radius * (scale + rate * (1.0 - scale)),
_paint);
}