代码:
int width = 1920;
int height = 1080;
Point2D center = new Point2D.Float(width / 2, height / 2);
float radius = height / 2;
float[] dist = {
0.0f, 1.0f };
//白色到透明色的渐变
Color[] colors = {
new Color(255,255,255), new Color(0,0,0, 0)};
RadialGradientPaint paint = new RadialGradientPaint(center, radius, dist, colors);
g2.setPaint(paint);
Shape shape = new Ellipse2D.Double(width / 2 - height / 2, 0, height, height);
AlphaComposite ac2 = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.04f * i);
g2.setComposite(ac2);
g2.fill(shape);
效果图如下: