尝试使用Java BufferedImage,Graphics将图像绘制到JFrame

Question

我正在尝试捕获屏幕,然后在缩放图像时递归地将图像绘制到JFrame(以创建当您在镜像中查看镜像时获得的效果).

我的代码有问题 - 它不会绘制任何图形.我究竟做错了什么？

import java.awt.AWTException;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.HeadlessException;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.BufferedImage;

import javax.swing.JFrame;


public class ScreenCapture extends JFrame {

    BufferedImage screenCapture;
    Graphics screenCaptureGraphics;
    private static int recurseCount = 0;
    private static float $scale = 0.9f;
    private static float scale = 1.0f;
    private static int height;
    private static int width;

    ScreenCapture() {
        try {
            screenCapture = new Robot().createScreenCapture(
                       new Rectangle(Toolkit.getDefaultToolkit().getScreenSize()) );
            height = screenCapture.getHeight();
            width = screenCapture.getWidth();
            setSize(new Dimension(width, height));
            addWindowListener(new LocalWindowListener());
            Graphics g = recursiveDraw(screenCapture, getGraphics());
            paint(g);
        } catch (HeadlessException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (AWTException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    private Graphics recursiveDraw(BufferedImage img, Graphics imgG) {
        updateScale(++recurseCount);
        float newWidth = scale*width;
        float newHeight = scale*height;
        int w = (int) newWidth;
        int h = (int) newHeight;
        System.out.println("W: " + w + "; H: " + h);
        if (w >= 10 && h >= 10) {
            //scale image
            System.out.print("Creating scaled Image...");
            Image scaled = img.getScaledInstance(w, h, Image.SCALE_SMOOTH);
            BufferedImage resized = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
            imgG = resized.createGraphics();
            imgG.drawImage(scaled, 0, 0, null);
            System.out.println("...Image drawn to graphics");
            //return new graphics
            return recursiveDraw(resized, imgG);
        } else {
            //otherwise return old graphics
            System.out.println("Completed.");
            return imgG;
        }
    }


    private void updateScale(int count) {
        for (int i=0; i<count; i++) {
            scale *= $scale;
        }
        System.out.println("Updated scale: " + scale + "; Recurse count: " + recurseCount);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new ScreenCapture().setVisible(true);
            }
        });
    }

    private class LocalWindowListener extends WindowAdapter {
        @Override
        public void windowClosing(WindowEvent e) {
            System.exit(0); return;
        }
    }

}

编辑: 这是我在@ andrew-thompson的答案之后尝试的:

ScreenCapture() {
    try {
        screenCapture = new Robot().createScreenCapture(
                   new Rectangle(Toolkit.getDefaultToolkit().getScreenSize()) );
        height = screenCapture.getHeight();
        width = screenCapture.getWidth();
        setSize(new Dimension(width, height));
        addWindowListener(new LocalWindowListener());
        setLayout(new GridLayout());
        add(new PaintPanel());
    } catch (HeadlessException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (AWTException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

private class PaintPanel extends JPanel {
    @Override
    public void paintComponent(Graphics g) {
        g=recursiveDraw(screenCapture, g);
        //what to do with g?
    }
}

我仍然有同样的问题,我不知道如何使BufferedImage绘制到图形.

Answer 1

将您的Swing代码与递归图像创建代码分开.实际上考虑创建一个静态方法,该方法创建并返回BufferedImage,并且其中没有Swing代码.然后让GUI在需要时调用方法,并获取图像并将其写入磁盘或在JLabel的ImageIcon中显示.

当我这样做(今天实际上)时,我用这个签名创建了一个递归方法

private static void recursiveDraw(BufferedImage img, Graphics imgG, double scale) { 

并使用此方法体(伪代码)

start recursiveDraw method 
   // most important: all recursions must have a good ending condition: 
   get img height and width. If either <= a min, return 
   create a BufferedImage, smlImg, for the smaller image using the height, 
        width and scale factor 
   Get the Graphics object, smlG, from the small image 
   Use smlG.drawImage(...) overload to draw the big image in shrunken 
        form onto the little image 
   recursively call recursiveDraw passing in smlImg, smlG, and scale. 
   dispose of smlG 
   draw smlImg (the small image) onto the bigger one using the bigger's 
        Graphics object (passed into this method) and a different 
        overload of the drawImage method. 
end recursiveDraw method

该算法产生如下图像:

例如:

import java.awt.*;
import java.awt.Dialog.ModalityType;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import javax.swing.*;

public class RecursiveDrawTest {
   private static final Color BACKGRND_1 = Color.green;
   private static final Color BACKGRND_2 = Color.MAGENTA;
   private static final Color FOREGRND_1 = Color.blue;
   private static final Color FOREGRND_2 = Color.RED;

   private static void createAndShowGui() {
      final JPanel mainPanel = new JPanel(new BorderLayout());
      final JSlider slider = new JSlider(50, 90, 65);
      slider.setMajorTickSpacing(10);
      slider.setMinorTickSpacing(5);
      slider.setPaintLabels(true);
      slider.setPaintTicks(true);

      JPanel southPanel = new JPanel();
      southPanel.add(new JLabel("Percent Size Reduction:"));
      southPanel.add(slider);
      southPanel.add(new JButton(new AbstractAction("Create Recursive Image") {

         @Override
         public void actionPerformed(ActionEvent arg0) {
            try {
               double scale = slider.getValue() / 100.0;
               BufferedImage img = createRecursiveImg(scale);
               ImageIcon icon = new ImageIcon(img);
               JLabel label = new JLabel(icon);

               Window win = SwingUtilities.getWindowAncestor(mainPanel);
               JDialog dialog = new JDialog(win, "Image", ModalityType.MODELESS);
               dialog.getContentPane().add(label);
               dialog.pack();
               dialog.setLocationRelativeTo(null);
               dialog.setVisible(true);
            } catch (AWTException e) {
               e.printStackTrace();
            }
         }
      }));

      mainPanel.add(new JScrollPane(new JLabel(new ImageIcon(createLabelImg()))), 
            BorderLayout.CENTER);
      mainPanel.add(southPanel, BorderLayout.PAGE_END);

      JFrame frame = new JFrame("RecursiveDrawTest");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   // create a background image to display in a JLabel so that the GUI
   // won't be boring.
   private static BufferedImage createLabelImg() {
      Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
      int width = (5 * d.width) / 6;
      int height = (5 * d.height) / 6;
      BufferedImage img = new BufferedImage(width, height, 
            BufferedImage.TYPE_INT_ARGB);
      Graphics2D g2 = img.createGraphics();
      g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
      g2.setPaint(new GradientPaint(0, 0, BACKGRND_1, 40, 40, BACKGRND_2, true));
      g2.fillRect(0, 0, width, height);
      g2.setPaint(new GradientPaint(0, height, FOREGRND_1, 40, height - 40, FOREGRND_2, true));
      g2.fillOval(0, 0, 2 * width, 2 * height);
      g2.dispose();
      return img;
   }

   // non-recursive image to get the initial image that will be drawn recursively
   public static BufferedImage createRecursiveImg(double scale) throws AWTException {
      Robot robot = new Robot();
      Dimension screenSz = Toolkit.getDefaultToolkit().getScreenSize();
      Rectangle screenRect = new Rectangle(screenSz);
      BufferedImage img = robot.createScreenCapture(screenRect);
      Graphics g = img.getGraphics();
      recursiveDraw(img, g, scale); // call recursive method
      g.dispose();
      return img;
   }

   // recursive method to draw image inside of image
   private static void recursiveDraw(BufferedImage img, Graphics g, double scale) {
      int w = img.getWidth();
      int h = img.getHeight();

      int smlW = (int)(w * scale);
      int smlH = (int)(h * scale);
      // criteria to end recursion
      if (smlW <= 1 || smlH <= 1) {
         return; 
      }

      BufferedImage smlImg = new BufferedImage(smlW, smlH, BufferedImage.TYPE_INT_ARGB);
      Graphics smlG = smlImg.getGraphics();
      // draw big image in little image, scaled to little image
      smlG.drawImage(img, 0, 0, smlW, smlH, null);

      // recursive call
      recursiveDraw(smlImg, smlG, scale);
      smlG.dispose(); // clear resources when done with them

      // these guys center the smaller img on the bigger
      int smlX = (w - smlW) / 2;
      int smlY = (h - smlH) / 2;
      // draw small img on big img
      g.drawImage(smlImg, smlX, smlY, smlW, smlH, null);
   }

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

Answer 2

 Graphics g = recursiveDraw(screenCapture, getGraphics());

不要打电话getGraphics().覆盖paint(Graphics)¹并使用提供的Graphics实例.

1. 使用Swing时,实际上最好覆盖paintComponent(Graphics)a JComponent或的方法JPanel.然后将其添加到顶级容器.