如何提高JPictureBox的大图绘制速度？

基本上，您希望将图像的缩放卸载到后台线程，缩放很耗时，并且您不想在事件调度线程的上下文中进行。

然后，这又引发了一些问题。除非确实需要，否则您不希望缩放图像，而实际上只想要最新的结果。

您可以设置一个小的单一重复计时器，而不必每次缩放都按比例缩放图像，每次您要进行更改时都会重置该计时器。这会将多个调整大小的请求合并为尽可能少的请求。本示例使用一个

javax.swing.Timer

接下来，它使用

ExecutorService

接下来，实际的缩放操作采用两步缩放，首先，它尝试做一个快速，低质量的缩放比例，可以将其快速显示在屏幕上，然后执行较慢的高质量的缩放比例，该缩放比例会在以后的某个时间进行更新…

import java.awt.Dimension;import java.awt.EventQueue;import java.awt.Graphics;import java.awt.Graphics2D;import java.awt.Image;import java.awt.Rectangle;import java.awt.RenderingHints;import java.awt.Transparency;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.event.KeyEvent;import java.awt.image.BufferedImage;import java.io.File;import java.io.IOException;import java.util.ArrayList;import java.util.List;import java.util.concurrent.Callable;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.Future;import javax.imageio.ImageIO;import javax.swing.AbstractAction;import javax.swing.ActionMap;import javax.swing.InputMap;import javax.swing.Jframe;import javax.swing.JPanel;import javax.swing.JScrollPane;import javax.swing.KeyStroke;import javax.swing.Scrollable;import javax.swing.SwingUtilities;import javax.swing.Timer;import javax.swing.UIManager;import javax.swing.UnsupportedLookAndFeelException;public class Test {    public static void main(String[] args) {        new Test();    }    public Test() {        EventQueue.invokeLater(new Runnable() { @Override public void run() {     try {         UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());     } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {         ex.printStackTrace();     }     Jframe frame = new Jframe("Testing");     frame.setDefaultCloseOperation(Jframe.EXIT_ON_CLOSE);     frame.add(new JScrollPane(new TestPane()));     frame.pack();     frame.setLocationRelativeTo(null);     frame.setVisible(true); }        });    }    public class TestPane extends JPanel implements Scrollable {        private BufferedImage master;        private Image scaled;        private double zoom = 1d;        private ExecutorService service;        private List<Future> scaleTasks;        private final Timer zoomTimer;        public TestPane() { scaleTasks = new ArrayList<>(5); service = Executors.newSingleThreadExecutor(); try {     master = ImageIO.read(new File("Some image some where"));     scaled = master; } catch (IOException ex) {     ex.printStackTrace(); } zoomTimer = new Timer(125, new ActionListener() {     @Override     public void actionPerformed(ActionEvent e) {         System.out.println("Update Zoom to " + getZoom());         updateToZoomFactor(getZoom());     } }); zoomTimer.setRepeats(false); InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW); ActionMap am = getActionMap(); im.put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0), "plus"); im.put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0), "minus"); am.put("plus", new AbstractAction() {     @Override     public void actionPerformed(ActionEvent e) {         double zoom = getZoom() + 0.1;         setZoom(zoom);     } }); am.put("minus", new AbstractAction() {     @Override     public void actionPerformed(ActionEvent e) {         double zoom = getZoom() - 0.1;         setZoom(zoom);     } });        }        @Override        public Dimension getPreferredSize() { return scaled == null      ? new Dimension(master.getWidth(), master.getHeight())      : new Dimension(scaled.getWidth(this), scaled.getHeight(this));        }        public BufferedImage getMaster() { return master;        }        public void setZoom(double value) { if (value < 0.1) {     value = 0.1; } else if (value > 2) {     value = 2d; } if (value != zoom) {     zoom = value;     zoomTimer.restart(); }        }        public double getZoom() { return zoom;        }        @Override        protected void paintComponent(Graphics g) { super.paintComponent(g); if (scaled != null) {     Graphics2D g2d = (Graphics2D) g.create();     int x = (getWidth() - scaled.getWidth(this)) / 2;     int y = (getHeight() - scaled.getHeight(this)) / 2;     g2d.drawImage(scaled, x, y, this);     g2d.dispose(); }        }        protected void setScaledResult(final Image image) { SwingUtilities.invokeLater(new Runnable() {     @Override     public void run() {         scaled = image;         invalidate();         revalidate();         repaint();     } });        }        protected void updateToZoomFactor(double zoom) { Future[] tasks = scaleTasks.toArray(new Future[scaleTasks.size()]); for (Future task : tasks) {     if (!task.isCancelled()) {         task.cancel(true);     } else {         scaleTasks.remove(task);     } } service.submit(new RescaleTask(zoom));        }        @Override        public Dimension getPreferredScrollableViewportSize() { return new Dimension(400, 400);        }        @Override        public int getScrollableUnitIncrement(Rectangle visibleRect, int orientation, int direction) { return 128;        }        @Override        public int getScrollableBlockIncrement(Rectangle visibleRect, int orientation, int direction) { return 128;        }        @Override        public boolean getScrollableTracksViewportWidth() { return false;        }        @Override        public boolean getScrollableTracksViewportHeight() { return false;        }        protected class RescaleTask implements Callable<Image> { private double zoom; protected RescaleTask(double zoom) {     this.zoom = zoom; } @Override public Image call() throws Exception {     if (zoom == 1) {         scaled = getMaster();     } else {         int width = (int) (getMaster().getWidth() * zoom);         int height = (int) (getMaster().getHeight() * zoom);         Image scaled = getMaster().getScaledInstance((int) width, (int) height, Image.SCALE_FAST);         if (!Thread.currentThread().isInterrupted()) {  setScaledResult(scaled);  if (zoom < 1) {      scaled = getScaledDownInstance(getMaster(), (int) width, (int) height);  } else {      scaled = getScaledUpInstance(getMaster(), (int) width, (int) height);  }  if (!Thread.currentThread().isInterrupted()) {      setScaledResult(scaled);  } else {      System.out.println("Was interrupted during quality scale");  }         } else {  System.out.println("Was interrupted during fast scale");         }     }     return scaled; } protected BufferedImage getScaledDownInstance(BufferedImage img,      int targetWidth,      int targetHeight) {     int type = (img.getTransparency() == Transparency.OPAQUE)          ? BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;     BufferedImage ret = (BufferedImage) img;     if (targetHeight > 0 || targetWidth > 0) {         int w = img.getWidth();         int h = img.getHeight();         do {  System.out.println(w + "x" + h + " -> " + targetWidth + "x" + targetHeight);  if (w > targetWidth) {      w /= 2;      if (w < targetWidth) {          w = targetWidth;      }  }  if (h > targetHeight) {      h /= 2;      if (h < targetHeight) {          h = targetHeight;      }  }  BufferedImage tmp = new BufferedImage(Math.max(w, 1), Math.max(h, 1), type);  Graphics2D g2 = tmp.createGraphics();  g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);  g2.drawImage(ret, 0, 0, w, h, null);  g2.dispose();  ret = tmp;         } while (w != targetWidth || h != targetHeight);     } else {         ret = new BufferedImage(1, 1, type);     }     return ret; } protected BufferedImage getScaledUpInstance(BufferedImage img,      int targetWidth,      int targetHeight) {     int type = BufferedImage.TYPE_INT_ARGB;     BufferedImage ret = (BufferedImage) img;     int w = img.getWidth();     int h = img.getHeight();     do {         if (w < targetWidth) {  w *= 2;  if (w > targetWidth) {      w = targetWidth;  }         }         if (h < targetHeight) {  h *= 2;  if (h > targetHeight) {      h = targetHeight;  }         }//          createCompatibleImage(w, h, type)         BufferedImage tmp = new BufferedImage(w, h, type);         Graphics2D g2 = tmp.createGraphics();         g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);         g2.drawImage(ret, 0, 0, w, h, null);         g2.dispose();         ret = tmp;         tmp = null;     } while (w != targetWidth || h != targetHeight);     return ret; }        }    }}

nb：这一点杀不死，但展示了一些关键思想

可能有帮助的其他事情之一是将图像转换为的兼容颜色模型

GraphicsDevice

 master = ImageIO.read(new File("Some image some where")); GraphicsDevice gd = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice(); GraphicsConfiguration gc = gd.getDefaultConfiguration(); BufferedImage compatible = gc.createCompatibleImage(master.getWidth(), master.getHeight(), Transparency.TRANSLUCENT); Graphics2D g2d = compatiable.createGraphics(); g2d.drawImage(master, 0, 0, this); g2d.dispose(); master = compatible;