Java Swing BufferedImage 质量差

Question

我正在尝试在 BufferedImage 上创建绘图，然后复制到 JPanel 上。当我直接在 JPanel 上绘制时，图片质量非常好，但是当使用中间 BufferedImage 时，质量/分辨率明显降低。我已经使用 OSX 的辅助功能面板中的缩放选项进行了检查。我正在 MacBook Pro Retina 上开发。

是否发生了某种自动缩放？我对 BufferedImage 做错了什么？

这是演示问题的代码

package com.sample.gui;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.Ellipse2D;
import java.awt.image.BufferedImage;

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

public class QualityProblem {

private static final double DOT_SIZE = 4;

public static void main(String[] args) {
    JFrame frame = new JFrame("ChartPanel demo");
    frame.setBackground(Color.WHITE);

    // JPanel draw = new DrawingOK();
    JPanel draw = new DrawingUgly();
    draw.setBackground(Color.BLACK);

    frame.getContentPane().add(draw, BorderLayout.CENTER);
    frame.setSize(new Dimension(1200, 900));
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    frame.setVisible(true);
}

private static class DrawingOK extends JPanel {

    private static final long serialVersionUID = 1L;

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        Graphics2D g2draw = (Graphics2D) g.create();
        try {
            g2draw.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            g2draw.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
            g2draw.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_PURE);

            Ellipse2D.Double e = new Ellipse2D.Double(50, 50, DOT_SIZE, DOT_SIZE);
            g2draw.setColor(Color.YELLOW);
            g2draw.fill(e);
        } finally {
            g2draw.dispose();
        }
    }
}

private static class DrawingUgly extends JPanel {

    private static final long serialVersionUID = 1L;

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        Dimension size = getParent().getSize();
        BufferedImage image = new BufferedImage(size.width, size.height, BufferedImage.TYPE_INT_RGB);

        Graphics2D ig = image.createGraphics();
        ig.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        ig.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
        ig.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_PURE);

        Graphics2D g2draw = (Graphics2D) g.create();
        try {
            Ellipse2D.Double e = new Ellipse2D.Double(50, 50, DOT_SIZE, DOT_SIZE);
            ig.setColor(Color.YELLOW);
            ig.fill(e);
            g2draw.drawImage(image, 0, 0, null);
        } finally {
            ig.dispose();
            g2draw.dispose();
        }
    }
}
}

编辑:添加了 4 像素点和 50D 放大的图像。丑陋的一个来自 BufferedImage 复制到屏幕的 Graphics

Answer 1

我修正了你的绘图代码。

这是丑陋的 GUI。

1. 我将面板的大小移到了面板构造函数中。设置框架大小包括边框。设置面板大小可为您提供所需的绘图区域。

2. 我将黑色背景绘制移到了 paintComponent 方法中。你还不如在一个地方完成所有的绘画。

3. 我清理了您的绘图代码。您无需复制 paintComponent 图形实例即可获取 Graphics2D。

4. 我把圆放大了，所以你可以看到清晰度。我将原点移到了圆心，并将 DOT_SIZE 变成了半径。

这是代码。

package com.ggl.testing;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.Ellipse2D;
import java.awt.image.BufferedImage;

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

public class QualityProblem implements Runnable {

    private static final double DOT_SIZE = 50D;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new QualityProblem());
    }

    @Override
    public void run() {
        JFrame frame = new JFrame("ChartPanel demo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setBackground(Color.WHITE);

        // JPanel draw = new DrawingOK();
        JPanel draw = new DrawingUgly();

        frame.getContentPane().add(draw, BorderLayout.CENTER);
        frame.pack();
        frame.setVisible(true);
    }

    private class DrawingOK extends JPanel {

        private static final long serialVersionUID = 1L;

        public DrawingOK() {
            this.setPreferredSize(new Dimension(600, 400));
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);

            Graphics2D g2draw = (Graphics2D) g;

            g2draw.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                    RenderingHints.VALUE_ANTIALIAS_ON);
            g2draw.setRenderingHint(RenderingHints.KEY_RENDERING,
                    RenderingHints.VALUE_RENDER_QUALITY);
            g2draw.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL,
                    RenderingHints.VALUE_STROKE_PURE);

            g2draw.setColor(Color.BLACK);
            g2draw.fillRect(0, 0, getWidth(), getHeight());

            Ellipse2D.Double e = new Ellipse2D.Double(300D - DOT_SIZE,
                    200D - DOT_SIZE, DOT_SIZE + DOT_SIZE, DOT_SIZE + DOT_SIZE);
            g2draw.setColor(Color.YELLOW);
            g2draw.fill(e);
        }
    }

    private class DrawingUgly extends JPanel {

        private static final long serialVersionUID = 1L;

        public DrawingUgly() {
            this.setPreferredSize(new Dimension(600, 400));
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);

            BufferedImage image = new BufferedImage(getWidth(), getHeight(),
                    BufferedImage.TYPE_INT_RGB);

            Graphics2D ig = image.createGraphics();
            ig.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                    RenderingHints.VALUE_ANTIALIAS_ON);
            ig.setRenderingHint(RenderingHints.KEY_RENDERING,
                    RenderingHints.VALUE_RENDER_QUALITY);
            ig.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL,
                    RenderingHints.VALUE_STROKE_PURE);

            ig.setColor(Color.BLACK);
            ig.fillRect(0, 0, getWidth(), getHeight());

            Ellipse2D.Double e = new Ellipse2D.Double(300D - DOT_SIZE,
                    200D - DOT_SIZE, DOT_SIZE + DOT_SIZE, DOT_SIZE + DOT_SIZE);
            ig.setColor(Color.YELLOW);
            ig.fill(e);
            ig.dispose();

            g.drawImage(image, 0, 0, this);
        }
    }

}