基于OpenCv和swing实现图片/视频的展示
图片的展示
swing展示图片，多为操作BufferedImage，这里要关注的核心是将Mat转为BufferedImage。
代码如下：
public Image toBufferedImage(Mat matrix) {
int type = BufferedImage.TYPE_BYTE_GRAY;
if (matrix.channels() > 1) {
type = BufferedImage.TYPE_3BYTE_BGR;
}
int bufferSize = matrix.channels() * matrix.cols() * matrix.rows();
byte[] buffer = new byte[bufferSize];
matrix.get(0,0,buffer); // get all the pixels
BufferedImage image = new BufferedImage(matrix.cols(),matrix.rows(),type);
final byte[] targetPixels = ((DataBufferByte)image.getRaster().getDataBuffer()).getData();
System.arraycopy(buffer,0,targetPixels,0,buffer.length);
return image;
}
comment 1：OpenCV Mat --> BufferedImage AWT ， 创建一个byte array用以保存mat 矩阵的像素信息。数组大小为通道数和图片宽/高之积。其中，Mat.get()将所有的元素导入byte数组。最终，图片的光栅信息通过 getDataBuffer()和getDate()组成接收数组，并通过System.arraycopy方法完成填充。实现最终的类型与数据的转移。
comment 2：图片/视频，最终展示的都为BufferedImage，并在JFrame中展示，这里可将toBufferedImage与swing组件配置以展示的部分抽取为类ImageReader。如下：
import org.opencv.core.Mat; import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferByte; /**
* @Author: nya
* @Description: 图片展示类
* @Date: Created in 10:55 2018/9/21
* @Modify by:
*/
public class ImageViewer {
private JLabel imageView; public void show(Mat image,String windowName) {
setSystemLookAndFeel();
JFrame frame = createJFrame(windowName);
Image loadedImage = toBufferedImage(image);
imageView.setIcon(new ImageIcon(loadedImage)); frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
} private JFrame createJFrame(String windowName) {
JFrame frame = new JFrame(windowName);
imageView = new JLabel();
final JScrollPane imageScrollPane = new JScrollPane(imageView);
imageScrollPane.setPreferredSize(new Dimension(640,480));
frame.add(imageScrollPane,BorderLayout.CENTER);
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
return frame;
} private void setSystemLookAndFeel() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (UnsupportedLookAndFeelException e) {
e.printStackTrace();
}
} public Image toBufferedImage(Mat matrix) {
int type = BufferedImage.TYPE_BYTE_GRAY;
if (matrix.channels() > 1) {
type = BufferedImage.TYPE_3BYTE_BGR;
}
int bufferSize = matrix.channels() * matrix.cols() * matrix.rows();
byte[] buffer = new byte[bufferSize];
matrix.get(0,0,buffer); // get all the pixels
BufferedImage image = new BufferedImage(matrix.cols(),matrix.rows(),type);
final byte[] targetPixels = ((DataBufferByte)image.getRaster().getDataBuffer()).getData();
System.arraycopy(buffer,0,targetPixels,0,buffer.length);
return image;
}
}
image Mat operate code：
String path = "src/main/java/com/opencv/simpleopencvsample/sample/1.jpg";
Mat openFile = null;
try {
// openFile just is path to mat
openFile = openFile(path);
Mat clone = openFile.clone();
System.out.println(openFile);
Imgproc.resize(openFile,clone,new Size(640,480));
System.out.println(clone);
ImageViewer imageViewer = new ImageViewer();
imageViewer.show(clone,"Loaded image"); } catch (Exception e) {
e.printStackTrace();
} finally {
// comment ： never forget to release the matrix
if (openFile != null ) {
openFile.release();
}
}
System.out.println(openFile);
视频的展示
有了图片展示为蓝本，视频的操作关键在于VideoCapture类的使用，展示部分不过是捕获视频的每一帧转为Mat，基于swing循环顺序展示即可。获取mat推荐采用read()，此方法为grab()/retrieve()的结合体。
为适应视频处理的JFrame宽高，此处自定义设置，主要采用toBufferedImage方法。
VideoCapture -> Mat -> display code:
import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.videoio.VideoCapture;
import org.opencv.videoio.Videoio; import javax.swing.*;
import java.awt.*; /**
* @Author: nya
* @Description: 视频捕获相关操作类VideoCapture使用
* @Date: Created in 13:50 2018/9/21
* @Modify by:
*/
public class VideoCaptureSample {
static {
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
}
private JFrame frame;
private JLabel imageLabel; public static void main(String[] args) {
VideoCaptureSample sample = new VideoCaptureSample();
sample.initGUI();
sample.runMainLoop(args);
} private void initGUI(){
frame = new JFrame("Camera Input Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(555,970);
imageLabel = new JLabel();
frame.add(imageLabel);
frame.setVisible(true);
} private void runMainLoop(String[] args) {
ImageViewer viewer = new ImageViewer();
Mat webcamMatImage = new Mat();
Image tempImage;
VideoCapture capture = new VideoCapture("src/main/java/com/opencv/simpleopencvsample/sample/1.mp4");
capture.set(Videoio.CAP_PROP_FRAME_WIDTH,550);
capture.set(Videoio.CAP_PROP_FRAME_HEIGHT,960);
if (capture.isOpened()) {
while (true) {
capture.read(webcamMatImage);
if (!webcamMatImage.empty()) {
tempImage = viewer.toBufferedImage(webcamMatImage);
ImageIcon imageIcon = new ImageIcon(tempImage,"Captured video");
imageLabel.setIcon(imageIcon);
frame.pack();
} else {
System.out.println(" --- Frame not captured -- Break !");
break;
}
}
} else {
System.out.println("Couldn't open capture.");
}
}
}
常见异常 VideoCapture-isOpened返回false
实际测试中，存在视频路径正常，isOpened()一直返回false的问题。
这是因为视频处理类VideoCapture位于opencv_videoio模块，使用该类时需在运行时加载预先构建的opencv_ffmpeg * .dll / so。该模块如果加载成功，ffmpeg可用于解码/编码视频；否则，使用其它API。在排除路径问题后，仍然无法读取视频则多为此情况。
解决方法很简单，将动态库dll/so导入 管理员/root 权限下配置的java.library.path路径下即可。