public void applyTo(Paint paint) {
    if (Color.alpha(color) > 0) {
      // Paint.setShadowLayer() removes the shadow if radius is 0, so we use a small nonzero value in that case
      paint.setShadowLayer(Math.max(radius, Float.MIN_VALUE), dx, dy, color);
    } else {
      paint.clearShadowLayer();
    }
  }
Applies a shadow to the provided Paint object.
lottie/src/main/java/com/airbnb/lottie/utils/DropShadow.java