基于Swing 实现放大镜效果

一：概述
本文代码在JDK6u20版本调试通过，通过对像素的抓取处理和利用TexturePaint对BufferedImage对象的支持
从而实现对任何JComponent组件的放大镜效果。

二：前期准备工作

1. 将传入的JComponent对象转换为BufferedImage对象做为源图像，有下面代码完成，关
键步骤在于从BufferedImage对象创建自己的图形设备对象

orginalImage = new BufferedImage(this.srcComponent.getSize().width, this.srcComponent.getSize().height, BufferedImage.TYPE_INT_ARGB); Graphics g = orginalImage.createGraphics(); this.srcComponent.paintAll(g);
2. 从源BufferedImage对象中读取所有的像素数据，这个在后面将会用到。代码如下

originalPixels = new int[orginalImage.getWidth()*orginalImage.getHeight()]; orginalImage.getRaster().getDataElements(0,0, orginalImage.getWidth(),
orginalImage.getHeight(), originalPixels)

3. 创建放大镜组件，使用一个自定义的JFrame对象，去掉边框，使用形状为圆形，实现代码如下：

zoomFrame = new JFrame("MagnifyGlass"); zoomFrame.setUndecorated(true); Shape shape = new Ellipse2D.Double(0, 0,180, 180); AWTUtilitiesWrapper.setWindowShape(zoomFrame,shape);

三：主要思路及关键代码

1. 捕获鼠标在源图像上的位置移动，这个需要完成MouseMotionListener接口，实现对位置捕获的代码如下：
double x = e.getPoint().getX(); double y = e.getPoint().getY();

2. 根据鼠标在源图像上的位置，抓取源图像上像素，抓取像素的范围取决于放缩的比例因子 // get garb area rectangle [b]int[/b] grabCols = (int)(([b]double[/b])mySize.width /zoomFactor); [b]int[/b] grabRows = ([b]int[/b])(([b]double[/b])mySize.height /zoomFactor);

3. 从源图像对象一维像素数组中获取要放大的三维像素数组，本实现的关键点之一，实现代码如下： 首先定义三维像素数组对象：
[b]int[/b][][][] data = new[b]int[/b][grabRows][grabCols][4];
转换为三维ARGB的像素数组：
// Alpha data data[row][col][0] = (aRow[col] >> 24) & 0xFF; // Red data data[row][col][1] = (aRow[col] >> 16) & 0xFF; // Green data data[row][col][2] = (aRow[col] >> 8) & 0xFF; // Blue data data[row][col][3]= (aRow[col]) & 0xFF;

4. 调用方法convertToOneDim()将抓取到的像素转换为一维数组，放入到创建的BufferedImage对象中，实现代码如下：
grabImage.getRaster().setDataElements( 0, 0,grabWidth, grabHeight, oneDimPixelData );

5.利用TexturePaint来使用grabImage对象来填充放大镜组件

TexturePaint tp = new TexturePaint((BufferedImage)grabImage,rect); g2.setPaint(tp); g2.fill(circle1);
6. 获得screen坐标来实现放大镜对鼠标的跟随效果

获取鼠标的screen坐标
// get screen point Point offsetPoint = srcComponent.getLocationOnScreen(); e.translatePoint(offsetPoint.x, offsetPoint.y); screenPoint = e.getPoint();

实现放大镜跟随鼠标效果：

zoomFrame.setLocation(screenPoint); zoomFrame.setAlwaysOnTop(true);

7.处理边缘像素放大问题，空白部分用白色填充
data[row][col][0] = 0xFF; // alpha

data[row][col][1] = 0xFF; // red

data[row][col][2] = 0xFF; // green

data[row][col][3] = 0xFF; // blue

8. 最终效果如下图：



全部源代码及测试程序如下：

import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Image; import java.awt.Paint; import java.awt.Point; import java.awt.RadialGradientPaint; import java.awt.Rectangle; import java.awt.RenderingHints; import java.awt.Shape; import java.awt.TexturePaint; import java.awt.event.MouseEvent; import java.awt.event.MouseMotionListener; import java.awt.geom.Ellipse2D; import java.awt.image.BufferedImage; import java.awt.image.ColorModel;  import javax.swing.JComponent; import javax.swing.JFrame;  public class PixelMagnifyGlass extends JComponent implements MouseMotionListener { 	 	/** 	 * magnify the image based on pixel data. 	 */ 	 	private static final long serialVersionUID = -1632282149543956832L; 	private double zoomFactor; 	private JComponent srcComponent; 	private Point imgPoint; 	private Point screenPoint; 	private JFrame zoomFrame; 	private Dimension mySize; 	private BufferedImage orginalImage; 	private int[] originalPixels; 	 	public PixelMagnifyGlass(JComponent comp, Dimension size, double zoom) { 		 this.srcComponent = comp; 		 screenPoint = new Point(-1, -1); 		 comp.addMouseMotionListener(this); 		 this.mySize = size; 		 this.zoomFactor = zoom; 		  		 // convert the JComponent to image 		 orginalImage = new BufferedImage(this.srcComponent.getSize().width,  				 		this.srcComponent.getSize().height, BufferedImage.TYPE_INT_ARGB); 		 Graphics g = orginalImage.createGraphics(); 		 this.srcComponent.paintAll(g); 		 g.dispose(); 		  		 // get all pixel arrays 		 originalPixels = new int[orginalImage.getWidth()*orginalImage.getHeight()]; 		 orginalImage.getRaster().getDataElements( 0, 0, orginalImage.getWidth(), orginalImage.getHeight(), originalPixels);  		  		 // start the glass component 		zoomFrame = new JFrame("MagnifyGlass"); 		zoomFrame.setUndecorated(true); 		Shape shape = new Ellipse2D.Double(0, 0,mySize.getWidth(), mySize.getHeight()); 		AWTUtilitiesWrapper.setWindowShape(zoomFrame, shape); 		  	} 	 	public void paint(Graphics g) { 		if(imgPoint.x == -1) { 			g.setColor(Color.BLUE); 			g.fillRect(0,0, mySize.width, mySize.height); 			return; 		} 		 		// draw zoom in/out image here 		Graphics2D g2 = (Graphics2D) g; 		g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); 		int grabWidth = (int)((double)mySize.width / zoomFactor); 		int grabHeight = (int)((double)mySize.height / zoomFactor); 		int[][][] threeDimPixelData = clipImageToThreeDim(originalPixels, (int)imgPoint.getX(), (int)imgPoint.getY()); 		int[] oneDimPixelData = convertToOneDim(threeDimPixelData, grabWidth, grabHeight); 		ColorModel cMD = orginalImage.getColorModel(); 		BufferedImage grabImage = new BufferedImage(orginalImage.getColorModel(), cMD.createCompatibleWritableRaster(grabWidth, grabHeight), cMD.isAlphaPremultiplied(), null); 		grabImage.getRaster().setDataElements( 0, 0, grabWidth, grabHeight, oneDimPixelData ); 		 		Image scaleImg = grabImage.getScaledInstance(mySize.width, mySize.height, Image.SCALE_FAST); 		// g2.drawImage(scaleImg, 0,0,null); 		 		// add glass edge with black 		Shape innerCircle = new Ellipse2D.Float(15.5f, 15.5f, mySize.width - 30, mySize.height - 30); 		Ellipse2D outterCircle = new Ellipse2D.Float(0, 0, mySize.width, mySize.height); 		Paint gp = new RadialGradientPaint((float)outterCircle.getCenterX(), (float)outterCircle.getCenterY(), 				 							(mySize.width)/2, 											new float[]{0f,0.8f,1f},new Color[]{Color.WHITE,Color.GRAY,Color.BLACK}); 		g2.setPaint(gp); 		g2.fill(outterCircle); 		Rectangle rect = new Rectangle(0,0,scaleImg.getWidth(null), scaleImg.getHeight(null)); 		TexturePaint tp = new TexturePaint((BufferedImage)grabImage, rect); 		g2.setPaint(tp); 		g2.fill(innerCircle); 	} 	 	public Dimension getPreferredSize() { 		return mySize; 	} 	 	public Dimension getMinimumSize() { 		return mySize; 	} 	 	public Dimension getMaximumSize() { 		return mySize; 	} 	 	 	@Override 	public void mouseDragged(MouseEvent e) { 		mouseMoved(e); 		 	} 	 	public int[][][] clipImageToThreeDim(int[] oneDPix, int startCols, int startRows) { 		 		// get garb area rectangle 		int grabCols = (int)((double)mySize.width / zoomFactor); 		int grabRows = (int)((double)mySize.height / zoomFactor); 		int[][][] data = new int[grabRows][grabCols][4]; 		 		for (int row = 0; row < grabRows; row++) { 			int[] aRow = new int[grabCols]; 			for (int col = 0; col < grabCols; col++) { 				int element = (row + startRows) * orginalImage.getWidth() + (startCols + col); 				 				// image edge detection and assign it as white color. 				if(element >= oneDPix.length || (startCols + col) >= orginalImage.getWidth()) { 					aRow[col] = 0; 				} else { 					aRow[col] = oneDPix[element]; 				} 			} 			 			for (int col = 0; col < grabCols; col++) { 				if(aRow[col] == 0) { 					// Alpha data 					data[row][col][0] = 0xFF; 					// Red data 					data[row][col][1] = 0xFF; 					// Green data 					data[row][col][2] = 0xFF; 					// Blue data 					data[row][col][3] = 0xFF; 				} else { 					// Alpha data 					data[row][col][0] = (aRow[col] >> 24) & 0xFF; 					// Red data 					data[row][col][1] = (aRow[col] >> 16) & 0xFF; 					// Green data 					data[row][col][2] = (aRow[col] >> 8) & 0xFF; 					// Blue data 					data[row][col][3] = (aRow[col]) & 0xFF; 				} 			} // end for loop on column  		} 		return data; 	} 	 	/* <p> The purpose of this method is to convert the data in the 3D array of ints back into </p> 	 * <p> the 1d array of type int. </p> 	 *  	 */ 	public int[] convertToOneDim(int[][][] data, int imgCols, int imgRows) { 		// Create the 1D array of type int to be populated with pixel data 		int[] oneDPix = new int[imgCols * imgRows * 4];  		// Move the data into the 1D array. Note the 		// use of the bitwise OR operator and the 		// bitwise left-shift operators to put the 		// four 8-bit bytes into each int. 		for (int row = 0, cnt = 0; row < imgRows; row++) { 			for (int col = 0; col < imgCols; col++) { 				oneDPix[cnt] = ((data[row][col][0] << 24) & 0xFF000000) 						| ((data[row][col][1] << 16) & 0x00FF0000) 						| ((data[row][col][2] << 8) & 0x0000FF00) 						| ((data[row][col][3]) & 0x000000FF); 				cnt++; 			}// end for loop on col  		}// end for loop on row  		return oneDPix; 	}// end convertToOneDim  	@Override 	public void mouseMoved(MouseEvent e) { 		double x = e.getPoint().getX(); 		double y = e.getPoint().getY(); 		 		//  we did not need to handle edge pixel like this again. 		//	if((x + mySize.getWidth()) > this.orginalImage.getWidth()) { 		//		x = x - ((x + mySize.getWidth()) - this.orginalImage.getWidth()); 		//	} 		//	if((y + mySize.getHeight()) > this.orginalImage.getHeight()) { 		//		y = y - ((y + mySize.getHeight()) - this.orginalImage.getHeight()); 		//	} 		//  end comment by gloomy fish on 15-October-2011 		 		imgPoint = new Point((int)x, (int)y); 		 		// get screen point 		Point offsetPoint = srcComponent.getLocationOnScreen(); 		e.translatePoint(offsetPoint.x, offsetPoint.y); 		screenPoint = e.getPoint(); 		repaint(); 		invokeGlass(); 	} 	 	/** 	 *  	 */ 	public void invokeGlass() { 		if(imgPoint.x == -1) { 			return; 		} 		 		if(zoomFrame.isVisible()) { 			zoomFrame.getContentPane().remove(this); 			zoomFrame.getContentPane().add(this); 			zoomFrame.setLocation(screenPoint); 		} else { 			zoomFrame.getContentPane().remove(this); 			zoomFrame.getContentPane().add(this); 			zoomFrame.pack(); 			zoomFrame.setLocation(screenPoint); 			zoomFrame.setVisible(true); 			zoomFrame.setAlwaysOnTop(true); 		} 	}  }

测试程序：

import java.awt.Dimension; import java.io.File;  import javax.swing.ImageIcon; import javax.swing.JFileChooser; import javax.swing.JFrame; import javax.swing.JLabel;  public class TestDetachedMagnifyingGlass { 	 	public TestDetachedMagnifyingGlass(File f) { 		ImageIcon i = new ImageIcon(f.getPath()); 		JLabel label = new JLabel(i); 		JFrame imageFrame = new JFrame("IMage"); 		imageFrame.getContentPane().add(label); 		imageFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 		imageFrame.pack(); 		imageFrame.setVisible(true); 		 		new PixelMagnifyGlass(label, new Dimension(180,180),2.0); 		// mag.invokeGlass(); 	} 	 	public static void main(String[] args) { 		JFileChooser chooser = new JFileChooser(); 		chooser.showOpenDialog(null); 		File f = chooser.getSelectedFile(); 		new TestDetachedMagnifyingGlass(f); 	}  }