OpenCV提供了一些基本的Webcam控制接口。用OpenCV C/C++或者Python,可以在任意平台快速创建一个摄像头预览应用。然而使用Java,情况就复杂的多,因为OpenCV Java并没有提供一个类似于imshow
的窗口显示接口。想要创建一个带界面的应用,就需要通过OpenCV接口获取数据,并转换成对应的格式,然后通过Java的UI组件显示出来。
在OpenCV官网下载最新的Windows安装包。
安装后找到目录opencv-4.3\opencv\build\java
。
如果用Eclipse,可以直接导入工程。如果用Maven,需要先安装到Maven的本地仓库:
mvn install:install-file -Dfile=opencv-430.jar -DgroupId=org -DartifactId=opencv -Dversion=4.3.0 -Dpackaging=jar
然后在pom.xml
文件里添加依赖:
org
opencv
4.3.0
还有一个问题就是dll文件怎么加载。如果找不到,会看到错误信息:
Exception in thread "main" java.lang.UnsatisfiedLinkError: no opencv_java430 in java.library.path
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1867)
at java.lang.Runtime.loadLibrary0(Runtime.java:870)
at java.lang.System.loadLibrary(System.java:1122)
at com.java.barcode.App.main(App.java:65)
解决方法有几种:
查看系统中的Java库加载路径。把dll文件放到对应的路径下即可:
System.out.println(System.getProperty("java.library.path"));
使用全路径加载:
System.load("D:/opencv-4.3/opencv/build/java/x64/opencv_java430.dll");
启动程序的时候指定dll路径:
java -Djava.library.path= -cp target/opencv-dotcode-1.0-SNAPSHOT-jar-with-dependencies.jar com.java.barcode.App
在OpenCV Java的文档中提供了一份基于JavaFX的示例代码。
参考逻辑之后,也可以把代码移植到Java Swing中。我这里用JLable
来显示视频帧:
public void updateViewer(final BufferedImage image) {
if (!SwingUtilities.isEventDispatchThread()) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
mImage.setIcon(new ImageIcon(image));
}
});
return;
}
}
Runnable frameGrabber = new Runnable() {
@Override
public void run() {
Mat frame = grabFrame();
byte[] data = Utils.matToByteArray(frame);
if (!status.get()) {
status.set(true);
barcodeTimer.schedule(new BarcodeRunnable(frame, mBarcodeReader, callback, status), 0, TimeUnit.MILLISECONDS);
}
BufferedImage bufferedImage = Utils.byteToBufferedImage(data, frame.width(), frame.height(), frame.channels());
if (isRunning) updateViewer(bufferedImage);
}
};
this.timer = Executors.newSingleThreadScheduledExecutor();
this.timer.scheduleAtFixedRate(frameGrabber, 0, 33, TimeUnit.MILLISECONDS);
OpenCV接口运行在独立的线程中,需要通过SwingUtilities
来更新UI。
在pom.xml
中添加Dynamsoft Barcode Reader SDK:
<repositories>
<repository>
<id>dbrid>
<url>https://download.dynamsoft.com/maven/dbr/jarurl>
repository>
repositories>
<dependencies>
<dependency>
<groupId>com.dynamsoftgroupId>
<artifactId>dbrartifactId>
<version>7.4.0version>
dependency>
dependencies>
然后像OpenCV一样创建一条线程来做条形码解码。
barcodeTimer = Executors.newSingleThreadScheduledExecutor();
Runnable
中的代码:
public void run() {
// TODO Auto-generated method stub
try {
TextResult[] results = reader.decodeBuffer(Utils.matToByteArray(frame), frame.width(), frame.height(), (int)frame.step1(), EnumImagePixelFormat.IPF_BGR_888, "");
if (results != null && results.length > 0) {
if (callback != null) {
callback.onResult(results, Utils.matToBufferedImage(frame));
}
}
else {
status.set(false);
}
} catch (BarcodeReaderException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
OpenCV获取的数据类型是Mat
。
条形码解码的时候要把Mat
转换成byte[]
:
public static byte[] matToByteArray(Mat original)
{
int width = original.width(), height = original.height(), channels = original.channels();
byte[] sourcePixels = new byte[width * height * channels];
original.get(0, 0, sourcePixels);
return sourcePixels;
}
而在显示画面的时候,要把数据再转成BufferedImage
:
public static BufferedImage byteToBufferedImage(byte[] sourcePixels, int width, int height, int channels)
{
BufferedImage image = null;
if (channels > 1)
{
image = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);
}
else
{
image = new BufferedImage(width, height, BufferedImage.TYPE_BYTE_GRAY);
}
final byte[] targetPixels = ((DataBufferByte) image.getRaster().getDataBuffer()).getData();
System.arraycopy(sourcePixels, 0, targetPixels, 0, sourcePixels.length);
return image;
}
最后通过自定义的JLable来绘制条形码的区域:
private ArrayList<Point[]> data = new ArrayList<>();
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
if (data.size() > 0) {
g2d.setColor(Color.RED);
for (Point[] points : data) {
for (int i = 0; i < points.length; ++i) {
if (i == 3) {
g2d.drawLine(points[i].x, points[i].y, points[0].x, points[0].y);
} else {
g2d.drawLine(points[i].x, points[i].y, points[i + 1].x, points[i + 1].y);
}
}
}
}
g2d.dispose();
}
public void appendPoints(Point[] points) {
data.add(points);
}
public void clearPoints() {
data.clear();
}
https://github.com/yushulx/java-dotcode-reader