使用SWT查看圖像

Question

我正在嘗試使用SWT製作圖像查看器，並在畫布上顯示圖像。單擊「下一步」按鈕時，我希望畫布上的圖像更改爲下一張圖像選擇文件夾。此外，我想通過使用在xml文件中呈現的矩形邊界在此圖像上繪製矩形。如何實現此目的？請幫助

Answer 1

下面是一個簡單的代碼（適用於圖像用正確的縱橫比萎縮等。]）

import java.io.IOException; 
import java.net.MalformedURLException; 
import java.net.URL; 
import java.util.Random; 

import org.eclipse.swt.SWT; 
import org.eclipse.swt.events.PaintEvent; 
import org.eclipse.swt.events.PaintListener; 
import org.eclipse.swt.events.SelectionAdapter; 
import org.eclipse.swt.events.SelectionEvent; 
import org.eclipse.swt.graphics.Color; 
import org.eclipse.swt.graphics.Image; 
import org.eclipse.swt.graphics.RGB; 
import org.eclipse.swt.graphics.Rectangle; 
import org.eclipse.swt.layout.FillLayout; 
import org.eclipse.swt.widgets.Button; 
import org.eclipse.swt.widgets.Composite; 
import org.eclipse.swt.widgets.Display; 
import org.eclipse.swt.widgets.Shell; 

public class ImageLoader { 

    private Display display = null; 
    private Shell shell = null; 
    private Composite imageCanvas = null; 
    private Image img = null; 
    private Random random = new Random(); 
    private Color rectColor = null; 

    private String[] imageURLs = new String[] { 
      "http://upload.wikimedia.org/wikipedia/en/7/70/Example.png", 
      "http://upload.wikimedia.org/wikipedia/commons/thumb/1/19/APEC_Police_Helicopter%2C_Opera_House%2C_2_Sept_2007.JPG/220px-APEC_Police_Helicopter%2C_Opera_House%2C_2_Sept_2007.JPG", 
      "http://upload.wikimedia.org/wikipedia/commons/thumb/a/a2/Abroad_-_1882.djvu/page13-474px-Abroad_-_1882.djvu.jpg" 
     }; 
    private int imgNum = 0; 
    private Rectangle[] rectangles = null; 

    public ImageLoader() { 
     display = new Display(); 
     shell = new Shell(display); 
     shell.setLayout(new FillLayout()); 
     shell.setSize(700, 500); 

     rectColor = new Color(display, new RGB(255, 0, 0)); 

     // load first image which should be displayed 
     loadImage(); 

     imageCanvas = new Composite(shell, SWT.BORDER); 
     // on each paint event (first view, window resize, redraw method, ...) make my code 
     imageCanvas.addPaintListener(new PaintListener() { 

      @Override 
      public void paintControl(PaintEvent e) { 
       // draw the image from (0,0) in it's own size 
       e.gc.drawImage(img, 0, 0); 

       // set foreground color (paint color) 
       e.gc.setForeground(rectColor); 
       // draw all loaded rectangles 
       for(int i = 0; i < rectangles.length; i++) e.gc.drawRectangle(rectangles[i]); 
      } 
     }); 

     Button btnNext = new Button(shell, SWT.PUSH); 
     btnNext.setText("Next image"); 
     btnNext.addSelectionListener(new SelectionAdapter() { 

      @Override 
      public void widgetSelected(SelectionEvent e) { 
       // load next image 
       loadImage(); 
       // repaint image canvas 
       imageCanvas.redraw(); 
      } 

     }); 

//  shell.pack(); 
     shell.open(); 
     while (!shell.isDisposed()) { 
      if (!display.readAndDispatch()) 
       display.sleep(); 
     } 

     rectColor.dispose(); 
    } 

    /** 
    * Loads next image from folder 
    */ 
    private void loadImage() { 
     try { 
      img = new Image(display, getImageURL().openStream()); 
     } catch (IOException ex) { 
      ex.printStackTrace(); 
     } 

     // read rectangles which should be shown 
     rectangles = new Rectangle[random.nextInt(5) + 3]; 
     for(int i = 0; i < rectangles.length; i++) rectangles[i] = getRectangleFromFile(); 
    } 

    /** 
    * Fakes loading next image from folder by cycling on image array 
    * @return 
    */ 
    private URL getImageURL() { 
     URL tmpURL; 
     try { 
      tmpURL = new URL(imageURLs[imgNum]); 
     } catch (MalformedURLException e) { 
      e.printStackTrace(); 
      return null; 
     } 
     // in the end? let's turn back on start 
     if(++imgNum >= imageURLs.length) imgNum = 0; 
     return tmpURL; 
    } 

    /** 
    * Fakes reading rectangles from file by generating random size and position rectangle 
    * @return 
    */ 
    private Rectangle getRectangleFromFile() { 
     return new Rectangle(random.nextInt(img.getBounds().width), random.nextInt(img.getBounds().height), random.nextInt(50), random.nextInt(50)); 
    } 

    public static void main(String[] args) { 
     new ImageLoader(); 
    } 
}