Java使用电脑摄像头识别二维码攻略
简介
本攻略主要介绍如何使用Java语言操作电脑摄像头，并借助相关库识别二维码。
准备工作
- 安装Java运行环境（JRE）
- 下载并安装Java开发工具（如Eclipse、IntelliJ IDEA等）
- 下载安装OpenCV库（可选，用于操作电脑摄像头）
操作电脑摄像头
方案一：使用JMF库
Java Media Framework（JMF）是Sun提供的一个库，它提供了一个便捷的方式来访问音频和视频文件。下面是一个使用JMF库来操作电脑摄像头获取图像的示例：
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.util.concurrent.Semaphore;
import javax.media.Buffer;
import javax.media.control.FrameGrabbingControl;
import javax.media.format.VideoFormat;
import javax.media.util.BufferToImage;
import com.sun.media.util.JMFSecurityManager;
import com.sun.media.util.SwingTimer;
import com.sun.media.util.ThreadExecutor;
public class CaptureDevice extends Thread implements FrameGrabbingControl {
private Component comp;
private Semaphore wait = new Semaphore(0);
private volatile Frame frame;
private Image image;
private VideoFormat defaultVideoFormat = new VideoFormat(VideoFormat.RGB);
private boolean saveInProgress = false;
private SwingTimer swingTimer;
private FrameGrabbingControl fgc;
private boolean runThread = true;
private int rate = 100;
private ThreadExecutor threader = new ThreadExecutor(0);
private boolean grabLoop = true;
private byte[] grabbuffer;
private Buffer buf = new Buffer();
private BufferToImage btoi = new BufferToImage(defaultVideoFormat);
private JMFSecurityManager security = null;
public CaptureDevice() {
super("Webcam Capture Thread");
}
public void initCapture(int width, int height) {
// 初始化设备
// ...
}
public synchronized void start() {
super.start();
if (swingTimer == null) {
swingTimer = new SwingTimer(rate, new Runnable() {
public void run() {
if (!saveInProgress) {
grabFrame();
}
}
});
swingTimer.start();
}
}
public synchronized void stop() {
super.stop();
if (swingTimer != null) {
swingTimer.stop();
swingTimer = null;
}
}
public void close() {
// 关闭设备
// ...
}
public void setComponent(Component comp) {
this.comp = comp;
}
public void setFormat(VideoFormat vf) {
}
public Component getControlComponent() {
return null;
}
public Object getControl(String controlName) {
return this;
}
public Object[] getControls() {
return new Object[0];
}
public synchronized Frame grabFrame() {
if (fgc != null) {
buf = new Buffer();
buf.setFormat(defaultVideoFormat);
try {
fgc.grabFrame(buf);
} catch (Exception ex) {
System.err.println("Could not grab frame: " + ex);
return null;
}
}
grabbuffer = (byte[]) buf.getData();
if (grabbuffer == null) {
return null;
}
if (image == null) {
Dimension size = comp.getSize();
if (size.width <= 0 || size.height <= 0) {
size = comp.getPreferredSize();
}
image = comp.createImage(size.width, size.height);
}
image = btoi.createImage(buf);
if (runThread) {
frame = new Frame((BufferedImage) image, System.currentTimeMillis());
wait.release();
return frame;
} else {
return null;
}
}
public synchronized Frame grabStillFrame() {
saveInProgress = true;
if (fgc != null) {
buf = new Buffer();
buf.setFormat(defaultVideoFormat);
try {
fgc.grabFrame(buf);
} catch (Exception ex) {
System.err.println("Could not grab frame: " + ex);
return null;
}
}
grabbuffer = (byte[]) buf.getData();
image = btoi.createImage(buf);
frame = new Frame((BufferedImage) image, System.currentTimeMillis());
saveInProgress = false;
return frame;
}
public void run() {
while (grabLoop) {
try {
wait.acquire();
if (frame != null) {
threader.execute(frame);
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
class Frame implements Runnable {
Thread t;
BufferedImage image;
long time;
public Frame(BufferedImage image, long time) {
this.image = image;
this.time = time;
t = new Thread(this);
t.start();
}
public void run() {
// 处理帧图像
// ...
}
}
}
方案二：使用OpenCV库
OpenCV是一款开源的计算机视觉库，支持多种平台和编程语言。Java版本的OpenCV提供了一个兼容Java的API，可以通过它来获取电脑摄像头的视频流。下面是一个使用OpenCV库来操作电脑摄像头获取图像的示例：
import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.MatOfByte;
import org.opencv.core.Size;
import org.opencv.core.Scalar;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.videoio.VideoCapture;
import org.opencv.imgproc.Imgproc;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.image.BufferedImage;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class VideoCaptureTest extends JPanel {
static{
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
}
private BufferedImage image;
public static void main(String args[]) {
JFrame frame = new JFrame("Video Capture Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
VideoCaptureTest vc = new VideoCaptureTest();
frame.setContentPane(vc);
frame.setVisible(true);
vc.capture();
}
public void paintComponent(Graphics g){
super.paintComponent(g);
if (this.image==null) return;
g.drawImage(this.image,10,10,this.image.getWidth(),this.image.getHeight(), null);
}
public void capture(){
VideoCapture capture = new VideoCapture(0);
capture.set(3,1280);
capture.set(4,720);
Mat webcam_image = new Mat();
MatToBufImg mat2Buf = new MatToBufImg();
if( capture.isOpened()){
while( true ){
capture.read(webcam_image);
MatOfByte matOfByte = new MatOfByte();
Imgcodecs.imencode(".jpg", webcam_image, matOfByte);
byte[] byteArray = matOfByte.toArray();
try {
image = mat2Buf.getImage(new Mat(matOfByte.toArray()), image);
repaint();
} catch(Exception e) {
e.printStackTrace();
}
}
}
}
}
class MatToBufImg {
Mat mat = new Mat();
BufferedImage img;
byte[] dat;
public BufferedImage getImage(Mat mat, BufferedImage img)
{
int width = mat.width(), height = mat.height(), channels = mat.channels() ;
dat = new byte[width * height * channels];
mat.get(0,0,dat);
if (img == null || img.getWidth() != width || img.getHeight() != height || img.getType() != BufferedImage.TYPE_3BYTE_BGR)
img = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);
final byte[] targetPixels = ((DataBufferByte) img.getRaster().getDataBuffer()).getData();
System.arraycopy(dat, 0, targetPixels, 0, dat.length);
return img;
}
}
识别二维码
Java提供了一些开源的库来识别二维码，比如Zxing和QR Code Library。我们在这里以Zxing库为例进行说明。首先需要在项目中添加Zxing库的依赖（可以通过Maven或手动添加jar包的方式实现），然后就可以调用相应的API接口来实现二维码的识别。下面是一个使用Zxing库来识别二维码的示例：
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;
import com.google.zxing.BinaryBitmap;
import com.google.zxing.LuminanceSource;
import com.google.zxing.MultiFormatReader;
import com.google.zxing.MultiFormatWriter;
import com.google.zxing.Result;
import com.google.zxing.WriterException;
import com.google.zxing.client.j2se.BufferedImageLuminanceSource;
import com.google.zxing.common.HybridBinarizer;
public class QRCode {
public static void main(String[] args) throws Exception {
// 生成二维码
String text = "http://www.baidu.com";
int width = 300;
int height = 300;
String format = "png";
MultiFormatWriter writer = new MultiFormatWriter();
BitMatrix matrix = writer.encode(text, BarcodeFormat.QR_CODE, width, height);
File outputFile = new File("qrcode.png");
MatrixToImageWriter.writeToFile(matrix, format, outputFile);
// 读取二维码
BufferedImage image = ImageIO.read(new File("qrcode.png"));
LuminanceSource source = new BufferedImageLuminanceSource(image);
BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source));
Result result = new MultiFormatReader().decode(bitmap);
System.out.println(result.getText());
}
}
总结
本攻略说明了Java使用电脑摄像头识别二维码的基本方法和实现过程，并提供了相关的代码示例供参考。读者可以根据自己的需求和场合来选择适当的方法和库实现相应的功能。
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