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Java Graphics2D浮点精确绘图椭圆形替代方案?

  •  3
  • thedarklord47  · 技术社区  · 8 年前

    因此,我试图绘制一条弧,并在其圆形端点周围放置一个圆,但由于舍入到最近的像素,我遇到了一些问题。这在某些情况下是可见的,但并非所有情况下都是如此。

    有没有一种方法可以使用浮点和抗锯齿绘制圆来消除这种舍入误差?

    import java.awt.*;
    import javax.swing.*;
    
    public class Example extends JFrame {
    
        private int CENTER = 200;
        private static int WINDOW = 400;
    
        private int LEFT = 50;
        private int TOP = 50;
        private int DIM = 300;
        private int DIAMETER = 26;
    
        public Example () {
            super();
        }
    
        public void paint (Graphics g) {
            Graphics2D g2 = (Graphics2D) g;
    
            g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    
            g2.setStroke(new BasicStroke(16, BasicStroke.CAP_ROUND, BasicStroke.JOIN_MITER));
            g2.setColor(new Color(0, 0, 255));
    
            g2.drawArc(LEFT, TOP, DIM, DIM, 0, 0);
            g2.drawArc(LEFT, TOP, DIM, DIM, 32, 0);
            g2.drawArc(LEFT, TOP, DIM, DIM, 115, 0);
            g2.drawArc(LEFT, TOP, DIM, DIM, 200, 0);
            g2.drawArc(LEFT, TOP, DIM, DIM, 331, 0);
    
            this.drawCircle(g2, 0);
            this.drawCircle(g2, 32);
            this.drawCircle(g2, 115);
            this.drawCircle(g2, 200);
            this.drawCircle(g2, 331);
    
            g2.setStroke(new BasicStroke(1));
            g2.setColor(new Color(0, 0, 0));
            g2.drawLine(0, CENTER, DIM * 2, CENTER);
            g2.drawLine(CENTER, 0, CENTER, DIM * 2);
        }
    
        private void drawCircle(Graphics2D g, int angle) {
            g.setStroke(new BasicStroke(3));
            g.setColor(new Color(0, 0, 255));
            g.drawOval(
                Math.round(CENTER + (float)(Math.cos(Math.toRadians(angle)) * (DIM/2)) - DIAMETER/2),
                Math.round(CENTER - (float)(Math.sin(Math.toRadians(angle)) * (DIM/2)) - DIAMETER/2),
                DIAMETER,
                DIAMETER
            );
        }
    
        public static void main (String args[]) {
            Example e = new Example();
            e.setSize(WINDOW, WINDOW);
            e.setVisible(true);
            e.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        }
    }
    
    1 回复  |  直到 8 年前
        1
  •  4
  •   Community Doug McClean    7 年前

    作为替代方案,请考虑 Ellipse2D 带有合适的 RenderingHints 显示了典型用法 here .

    Ellipse2D circle = new Ellipse2D.Float(…);
    Graphics2D g2d = (Graphics2D) g;
    g2d.setRenderingHints(…);
    g2d.fill(circle);
    

    因为各种各样 渲染提示 依赖于实现,下面的示例将让您单独评估效果。

    image

    import java.awt.BasicStroke;
    import java.awt.Dimension;
    import java.awt.EventQueue;
    import java.awt.Graphics;
    import java.awt.Graphics2D;
    import java.awt.RenderingHints;
    import java.awt.geom.Ellipse2D;
    import javax.swing.JFrame;
    import javax.swing.JPanel;
    
    /**
     * @see https://stackoverflow.com/a/38669048/230513
     */
    public class Test {
    
        private void display() {
            JFrame f = new JFrame("Test");
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            f.add(new JPanel() {
                private static final int N = 8;
                private final Ellipse2D ellipse = new Ellipse2D.Float();
    
                @Override
                protected void paintComponent(Graphics g) {
                    super.paintComponent(g);
                    Graphics2D g2d = (Graphics2D) g;
                    g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                        RenderingHints.VALUE_ANTIALIAS_ON);
                    g2d.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL,
                        RenderingHints.VALUE_STROKE_PURE);
                    g2d.setStroke(new BasicStroke(N));
                    ellipse.setFrame(N, N, getWidth() - 2 * N, getHeight() - 2 * N);
                    g2d.draw(ellipse);
                }
    
                @Override
                public Dimension getPreferredSize() {
                    return new Dimension(320, 240);
                }
            });
            f.pack();
            f.setLocationRelativeTo(null);
            f.setVisible(true);
        }
    
        public static void main(String[] args) {
            EventQueue.invokeLater(new Test()::display);
        }
    }