java 生成二维码原理分析

1.首先把java生成二维码的代码贴出来。

public class QRCodeUtil {
private static final Logger logger = LoggerFactory
.getLogger(QRCodeUtil.class);
private static final String CHARSET = "utf-8";
private static final String FORMAT_NAME = "JPG";
// 二维码尺寸
private static final int QRCODE_SIZE = 200;
// LOGO宽度
private static final int WIDTH = 80;
// LOGO高度
private static final int HEIGHT = 80;


private static BufferedImage createImage(String content, String imgPath,
boolean needCompress) throws Exception {
Hashtable<EncodeHintType, Object> hints = new Hashtable<EncodeHintType, Object>();
hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.H);
hints.put(EncodeHintType.CHARACTER_SET, CHARSET);
hints.put(EncodeHintType.MARGIN, 1);
BitMatrix bitMatrix = new MultiFormatWriter().encode(content,
BarcodeFormat.QR_CODE, QRCODE_SIZE, QRCODE_SIZE, hints);
int width = bitMatrix.getWidth();
int height = bitMatrix.getHeight();
BufferedImage image = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
image.setRGB(x, y, bitMatrix.get(x, y) ? 0xFF000000
: 0xFFFFFFFF);
}
}
if (imgPath == null || "".equals(imgPath)) {
return image;
}
// 插入图片
QRCodeUtil.insertImage(image, imgPath, needCompress);
return image;
}


/**
* 插入LOGO
* 
* @param source
*            二维码图片
* @param imgPath
*            LOGO图片地址
* @param needCompress
*            是否压缩
* @throws Exception
*/
private static void insertImage(BufferedImage source, String imgPath,
boolean needCompress) throws Exception {
File file = new File(imgPath);
if (!file.exists()) {
logger.info(""+imgPath+"   该文件不存在！");
return;
}
Image src = ImageIO.read(new File(imgPath));
int width = src.getWidth(null);
int height = src.getHeight(null);
if (needCompress) { // 压缩LOGO
if (width > WIDTH) {
width = WIDTH;
}
if (height > HEIGHT) {
height = HEIGHT;
}
Image image = src.getScaledInstance(width, height,
Image.SCALE_SMOOTH);
BufferedImage tag = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);
Graphics g = tag.getGraphics();
g.drawImage(image, 0, 0, null); // 绘制缩小后的图
g.dispose();
src = image;
}
// 插入LOGO
Graphics2D graph = source.createGraphics();
int x = (QRCODE_SIZE - width) / 2;
int y = (QRCODE_SIZE - height) / 2;
graph.drawImage(src, x, y, width, height, null);
Shape shape = new RoundRectangle2D.Float(x, y, width, width, 6, 6);
graph.setStroke(new BasicStroke(3f));
graph.draw(shape);
graph.dispose();
}


/**
* 生成二维码(内嵌LOGO)
* 
* @param content
*            内容
* @param imgPath
*            LOGO地址
* @param destPath
*            存放地址
* @param needCompress
*            是否压缩LOGO
* @throws Exception
*/
public static void encode(String content, String imgPath, String destPath,
boolean needCompress) throws Exception {
BufferedImage image = QRCodeUtil.createImage(content, imgPath,
needCompress);
File file = new File(destPath);
if(!file.getParentFile().exists()){
file.getParentFile().mkdirs();
}
ImageIO.write(image, FORMAT_NAME, file);
}


/**
* 当文件夹不存在时，mkdirs会自动创建多层目录，区别于mkdir．(mkdir如果父目录不存在则会抛出异常)
* @author chenyc
* @date 2015-4-27 上午10:16:36
* @param destPath 存放目录
*/
public static void mkdirs(String destPath) {
File file =new File(destPath);    
//当文件夹不存在时，mkdirs会自动创建多层目录，区别于mkdir．(mkdir如果父目录不存在则会抛出异常)
if (!file.exists() && !file.isDirectory()) {
file.mkdirs();
}
}


/**
* 生成二维码(内嵌LOGO)
* 
* @param content
*            内容
* @param imgPath
*            LOGO地址
* @param destPath
*            存储地址
* @throws Exception
*/
public static void encode(String content, String imgPath, String destPath)
throws Exception {
QRCodeUtil.encode(content, imgPath, destPath, false);
}


/**
* 生成二维码
* 
* @param content
*            内容
* @param destPath
*            存储地址
* @param needCompress
*            是否压缩LOGO
* @throws Exception
*/
public static void encode(String content, String destPath,
boolean needCompress) throws Exception {
QRCodeUtil.encode(content, null, destPath, needCompress);
}


/**
* 生成二维码
* 
* @param content
*            内容
* @param destPath
*            存储地址
* @throws Exception
*/
public static void encode(String content, String destPath) throws Exception {
QRCodeUtil.encode(content, null, destPath, false);
}


/**
* 生成二维码(内嵌LOGO)
* 
* @param content
*            内容
* @param imgPath
*            LOGO地址
* @param output
*            输出流
* @param needCompress
*            是否压缩LOGO
* @throws Exception
*/
public static void encode(String content, String imgPath,
OutputStream output, boolean needCompress) throws Exception {
BufferedImage image = QRCodeUtil.createImage(content, imgPath,
needCompress);
ImageIO.write(image, FORMAT_NAME, output);
}


/**
* 生成二维码
* 
* @param content
*            内容
* @param output
*            输出流
* @throws Exception
*/
public static void encode(String content, OutputStream output)
throws Exception {
QRCodeUtil.encode(content, null, output, false);
}


/**
* 解析二维码
* 
* @param file
*            二维码图片
* @return
* @throws Exception
*/
public static String decode(File file) throws Exception {
BufferedImage image;
image = ImageIO.read(file);
if (image == null) {
return null;
}
BufferedImageLuminanceSource source = new BufferedImageLuminanceSource(
image);
BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source));
Result result;
Hashtable<DecodeHintType, Object> hints = new Hashtable<DecodeHintType, Object>();
hints.put(DecodeHintType.CHARACTER_SET, CHARSET);
result = new MultiFormatReader().decode(bitmap, hints);
String resultStr = result.getText();
return resultStr;
}


/**
* 解析二维码
* 
* @param path
*            二维码图片地址
* @return
* @throws Exception
*/
public static String decode(String path) throws Exception {
return QRCodeUtil.decode(new File(path));
}


public static void main(String[] args) throws Exception {
String text = "http://itunes.apple.com/cn/app/beng-huai-xue-yuan2/id737651307?mt=8";
QRCodeUtil.encode(text, "D:/temp2/and_ewm.png", "D:/temp2/and.png", true);
}

   解析二维码时需要的辅助类

  public class BufferedImageLuminanceSource extends LuminanceSource {
private final BufferedImage image;
private final int left;
private final int top;


public BufferedImageLuminanceSource(BufferedImage image) {
this(image, 0, 0, image.getWidth(), image.getHeight());
}


public BufferedImageLuminanceSource(BufferedImage image, int left,
int top, int width, int height) {
super(width, height);


int sourceWidth = image.getWidth();
int sourceHeight = image.getHeight();
if (left + width > sourceWidth || top + height > sourceHeight) {
throw new IllegalArgumentException(
"Crop rectangle does not fit within image data.");
}


for (int y = top; y < top + height; y++) {
for (int x = left; x < left + width; x++) {
if ((image.getRGB(x, y) & 0xFF000000) == 0) {
image.setRGB(x, y, 0xFFFFFFFF); // = white
}
}
}


this.image = new BufferedImage(sourceWidth, sourceHeight,
BufferedImage.TYPE_BYTE_GRAY);
this.image.getGraphics().drawImage(image, 0, 0, null);
this.left = left;
this.top = top;
}



public byte[] getRow(int y, byte[] row) {
if (y < 0 || y >= getHeight()) {
throw new IllegalArgumentException(
"Requested row is outside the image: " + y);
}
int width = getWidth();
if (row == null || row.length < width) {
row = new byte[width];
}
image.getRaster().getDataElements(left, top + y, width, 1, row);
return row;
}



public byte[] getMatrix() {
int width = getWidth();
int height = getHeight();
int area = width * height;
byte[] matrix = new byte[area];
image.getRaster().getDataElements(left, top, width, height, matrix);
return matrix;
}



public boolean isCropSupported() {
return true;
}



public LuminanceSource crop(int left, int top, int width, int height) {
return new BufferedImageLuminanceSource(image, this.left + left,
this.top + top, width, height);
}



public boolean isRotateSupported() {
return true;
}



public LuminanceSource rotateCounterClockwise() {
int sourceWidth = image.getWidth();
int sourceHeight = image.getHeight();
AffineTransform transform = new AffineTransform(0.0, -1.0, 1.0,
0.0, 0.0, sourceWidth);
BufferedImage rotatedImage = new BufferedImage(sourceHeight,
sourceWidth, BufferedImage.TYPE_BYTE_GRAY);
Graphics2D g = rotatedImage.createGraphics();
g.drawImage(image, transform, null);
g.dispose();
int width = getWidth();
return new BufferedImageLuminanceSource(rotatedImage, top,
sourceWidth - (left + width), getHeight(), width);
}

 我们主要使用类是QRCodeUtil

     生成二维码调用的方法是

      QRCodeUtil.encode(text, "D:/temp2/and_ewm.png", "D:/temp2/and.png", true);

     text：文本内容，一般会放链接地址

    D:/temp2/and_ewm.png：内嵌logo地址

    D:/temp2/and.png：生成二维码地址

    true：是否压缩logo图片

  下面我们来分析下encode方法。

  首先调用了createImage方法，来创建二维码整体图片。

  BufferedImage image = QRCodeUtil.createImage(content, imgPath,
needCompress);

 在createImage方法中开始只是创建二维码外围的整体图片：

 BitMatrix bitMatrix = new MultiFormatWriter().encode(content,
BarcodeFormat.QR_CODE, QRCODE_SIZE, QRCODE_SIZE, hints);
int width = bitMatrix.getWidth();
int height = bitMatrix.getHeight();
BufferedImage image = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
image.setRGB(x, y, bitMatrix.get(x, y) ? 0xFF000000
: 0xFFFFFFFF);
}
}

 如果单独使用这段而不使用他下面的内容，我们也能创建出来二维码，只是这个二维码不带logo图案。

 创建图片使用的是java下awt包中的BufferedImage类，专门用于图片流描述的类。

 接下来是往这个图片流中插入logo图

 // 插入图片
 QRCodeUtil.insertImage(image, imgPath, needCompress);

 调用了insertImage方法

 在这个方法中我们能看到创建图片的最终实现方法。

 使用的也是awt包下的Graphics2D类。

 该类是创建图片的专用类。

 首先我们创建一个Graphics2D对象Graphics2D graph = source.createGraphics();

 然后把logo图片放到这个对象中graph.drawImage(src, x, y, width, height, null);

 最后生成图片graph.draw(shape);

 最后一步我们要做的就是把生成的图片读入到文件中。

ImageIO.write(image, FORMAT_NAME, file);