SWT中怎样改变图片大小？


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.Image;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.FileDialog;
import org.eclipse.swt.widgets.Shell;public class ImageTest { private String fileName = null; private Image image = null; private Canvas canvas; public static void main(String[] args) {
try {
ImageTest window = new ImageTest();
window.open();
} catch (Exception e) {
e.printStackTrace();
}
} public void open() { 
        final Display display = Display.getDefault(); 
        final Shell shell = new Shell(); 
        shell.setSize(309, 314); 
        shell.setText("SWT Application"); 
        shell.open();         Button button_Scan = new Button(shell, SWT.NONE); 
        button_Scan.setText("浏览"); 
        button_Scan.setBounds(3, 3, 55, 25); 
        button_Scan.addSelectionListener(new SelectionAdapter() { 
            public void widgetSelected(final SelectionEvent e) { 
                FileDialog dlg =new FileDialog(shell, SWT.OPEN); 
                dlg.setText("Open"); 
                dlg.setFilterNames(new String[]{"图片文件(*.jpg)","图片文件（*.gif）"}); 
                dlg.setFilterExtensions(new String[]{"*.jpg", "*.gif"}); 
                fileName = dlg.open();//取得打开图片的物理地址 
                if (fileName!=null){ 
                    image = new Image(null, fileName); 
                    canvas.redraw(); 
                } 
            } 
        });         canvas = new Canvas(shell, SWT.BORDER); 
        canvas.setBounds(0, 29, 300, 256); 
        canvas.addPaintListener(new PaintListener(){ 
            public void paintControl(PaintEvent arg0) { 
                if (image != null) { 
                    arg0.gc.drawImage(image, 0, 0); 
                } 
            }
        });         shell.layout(); 
        while (!shell.isDisposed()) { 
            if (!display.readAndDispatch()) 
                display.sleep(); 
        } 
}
}这是在网上找的一段代码，但是如果图片过大，就只会显示一部分
怎么样能把图片缩小后再放到image中呢
谢过！