矩形渐变

Question

我正试图在我的用户界面中实现一个draw(Graphics2D g)方法。它不是一个摇摆组件，我正在自己做画。我想创建一个渐变边框这样的形象

怎样绘制类似于一个梯度？

Answer 1

你真的不指定你想要什么，但如果是我认为它，那么它有点类似于我在my answer to "How to make gradient border of an image using java?"写道。

这里的技巧是不创建单个渐变颜料，并且不填充单个形状。相反，必须用梯度填充的区域分为8个部分：四个边和四个角。边缘用简单的渐变涂料填充。角落里充满了径向渐变涂料。然后它只是摆弄坐标，但这可以用一种相当通用的方式完成，当内部形状被给出为Rectangle2D。

然而，结果可能的话，例如，像这样：

import java.awt.Color; 
import java.awt.Dimension; 
import java.awt.GradientPaint; 
import java.awt.Graphics; 
import java.awt.Graphics2D; 
import java.awt.MultipleGradientPaint.CycleMethod; 
import java.awt.RadialGradientPaint; 
import java.awt.Shape; 
import java.awt.geom.Point2D; 
import java.awt.geom.Rectangle2D; 
import java.awt.geom.RoundRectangle2D; 

import javax.swing.JFrame; 
import javax.swing.JPanel; 
import javax.swing.SwingUtilities; 

public class RectangularGradientTest 
{ 
    public static void main(String[] args) 
    { 
     SwingUtilities.invokeLater(new Runnable() 
     { 
      @Override 
      public void run() 
      { 
       createAndShowGUI(); 
      } 
     }); 
    } 

    private static void createAndShowGUI() 
    { 
     JFrame f = new JFrame(); 
     f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     f.getContentPane().add(new RectangularGradientTestPanel()); 
     f.pack(); 
     f.setLocationRelativeTo(null); 
     f.setVisible(true); 
    } 
} 


class RectangularGradientTestPanel extends JPanel 
{ 
    @Override 
    protected void paintComponent(Graphics gr) 
    { 
     super.paintComponent(gr); 
     Graphics2D g = (Graphics2D)gr; 
     Rectangle2D r = new Rectangle2D.Double(100,100,200,100); 
     draw(g, r, 75); 

     Shape rr = new RoundRectangle2D.Double(80,80,240,140,20,20); 
     g.setColor(Color.BLACK); 
     g.fill(rr); 
    } 

    @Override 
    public Dimension getPreferredSize() 
    { 
     if (isPreferredSizeSet()) 
     { 
      return super.getPreferredSize(); 
     } 
     return new Dimension(400,300); 
    } 


    private static void draw(Graphics2D g, Rectangle2D r, double s) 
    { 
     Color c0 = new Color(255,0,0); 
     Color c1 = new Color(255,0,0,0); 

     double x0 = r.getMinX(); 
     double y0 = r.getMinY(); 
     double x1 = r.getMaxX(); 
     double y1 = r.getMaxY(); 
     double w = r.getWidth(); 
     double h = r.getHeight(); 

     // Left 
     g.setPaint(new GradientPaint(
      new Point2D.Double(x0, y0), c0, 
      new Point2D.Double(x0 - s, y0), c1)); 
     g.fill(new Rectangle2D.Double(x0 - s, y0, s, h)); 

     // Right 
     g.setPaint(new GradientPaint(
      new Point2D.Double(x1, y0), c0, 
      new Point2D.Double(x1 + s, y0), c1)); 
     g.fill(new Rectangle2D.Double(x1, y0, s, h)); 

     // Top 
     g.setPaint(new GradientPaint(
      new Point2D.Double(x0, y0), c0, 
      new Point2D.Double(x0, y0 - s), c1)); 
     g.fill(new Rectangle2D.Double(x0, y0 - s, w, s)); 

     // Bottom 
     g.setPaint(new GradientPaint(
      new Point2D.Double(x0, y1), c0, 
      new Point2D.Double(x0, y1 + s), c1)); 
     g.fill(new Rectangle2D.Double(x0, y1, w, s)); 

     float fractions[] = new float[] { 0.0f, 1.0f }; 
     Color colors[] = new Color[] { c0, c1 }; 

     // Top Left 
     g.setPaint(new RadialGradientPaint(
      new Rectangle2D.Double(x0 - s, y0 - s, s + s, s + s), 
      fractions, colors, CycleMethod.NO_CYCLE)); 
     g.fill(new Rectangle2D.Double(x0 - s, y0 - s, s, s)); 

     // Top Right 
     g.setPaint(new RadialGradientPaint(
      new Rectangle2D.Double(x1 - s, y0 - s, s + s, s + s), 
      fractions, colors, CycleMethod.NO_CYCLE)); 
     g.fill(new Rectangle2D.Double(x1, y0 - s, s, s)); 

     // Bottom Left 
     g.setPaint(new RadialGradientPaint(
      new Rectangle2D.Double(x0 - s, y1 - s, s + s, s + s), 
      fractions, colors, CycleMethod.NO_CYCLE)); 
     g.fill(new Rectangle2D.Double(x0 - s, y1, s, s)); 

     // Bottom Right 
     g.setPaint(new RadialGradientPaint(
      new Rectangle2D.Double(x1 - s, y1 - s, s + s, s + s), 
      fractions, colors, CycleMethod.NO_CYCLE)); 
     g.fill(new Rectangle2D.Double(x1, y1, s, s)); 
    } 

}