有时我们需要在后台自动拉取 rtsp、rtmp 等视频流并进行截图，这个使用 javaCV 库即可实现。javaCV 之所以叫 javaCV 就是因为 openCV 而得名，不过 javaCV 的功能远远大于 openCV，openCV 只能用于处理图像，而 javacv 不仅包含 openCV 全套 api，还支持 ffmpeg 音视频编解码，tensflow、caffe 等深度学习库，tessrac ocr 等字符识别，矩阵计算库。下面我通过样例演示如何使用 javaCV。

1，安装配置

<dependency>
        <groupId>org.bytedeco</groupId>
        <artifactId>javacv-platform</artifactId>
        <version>1.5.7</version>
</dependency>

2，使用样例

public class VideoCapture {
  public static void main(String[] args)  {
    // 视频路径
    String url = "rtmp://ns8.indexforce.com/home/mystream";
    // 保存路径
    String savePath = "/Users/hangge/Desktop/" + System.currentTimeMillis() + ".jpg";

    try {
      // 开始截图
      startCaputre(url, savePath);
    } catch (IOException e) {
      throw new RuntimeException(e);
    } catch (InterruptedException e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * 开始截图
   */
  public static void startCaputre(String url, String savePath)
          throws IOException, InterruptedException{
    FFmpegFrameGrabber grabber = FFmpegFrameGrabber.createDefault(url);
    grabber.setOption("rtsp_transport", "tcp"); // 使用tcp的方式，不然会丢包很严重
    //grabber.setImageWidth(960); //设置宽高尺寸（不设置则使用视频流原始宽高）
    //grabber.setImageHeight(540);
    System.out.println("--- grabber start ---");
    grabber.start();
    while (true){
      Frame frame = grabber.grabImage();
      if (frame != null) {
        File outPut = new File(savePath);
        ImageIO.write(frameToBufferedImage(frame), "jpg", outPut);
        grabber.stop();
        grabber.release();
        System.out.println("图片已保存：" + outPut.getPath());
        System.out.println("--- grabber end ---");
        break;
      }
    }
  }

  /**
   * 创建BufferedImage对象
   */
  public static BufferedImage frameToBufferedImage(Frame frame) {
    Java2DFrameConverter converter = new Java2DFrameConverter();
    BufferedImage bufferedImage = converter.getBufferedImage(frame);
    return bufferedImage;
  }
}

（2）运行结构如下，可以看到视频图片已经成功保存到本地：

附一：实现视频的连续截图

public class VideoCapture {
  public static void main(String[] args)  {
    // 视频路径
    String url = "rtmp://ns8.indexforce.com/home/mystream";
    // 保存路径
    String savePath = "/Users/hangge/Desktop/";

    try {
      // 开始截图（每5秒截取一张图片，总共10张）
      startCaputre(url, savePath, 5, 10);
    } catch (IOException e) {
      throw new RuntimeException(e);
    } catch (InterruptedException e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * 开始截图
   */
  public static void startCaputre(String url, String savePath, int interval, int total)
          throws IOException, InterruptedException{
    FFmpegFrameGrabber grabber = FFmpegFrameGrabber.createDefault(url);
    grabber.setOption("rtsp_transport", "tcp"); // 使用tcp的方式，不然会丢包很严重
    //grabber.setImageWidth(960); //设置宽高尺寸（不设置则使用视频流原始宽高）
    //grabber.setImageHeight(540);
    System.out.println("--- grabber start ---");
    grabber.start();
    while (total>0){
      Frame frame = grabber.grabImage();
      if (frame != null) {
        File outPut = new File(savePath + System.currentTimeMillis() + ".jpg");
        ImageIO.write(frameToBufferedImage(frame), "jpg", outPut);
        System.out.println("图片已保存：" + outPut.getPath());
        total--;
        Thread.sleep(interval * 1000);
      }
    }
    grabber.stop();
    grabber.release();
    System.out.println("--- grabber end ---");
  }

  /**
   * 创建BufferedImage对象
   */
  public static BufferedImage frameToBufferedImage(Frame frame) {
    Java2DFrameConverter converter = new Java2DFrameConverter();
    BufferedImage bufferedImage = converter.getBufferedImage(frame);
    return bufferedImage;
  }
}

（2）运行结果如下：

附二：对外提供接口服务

@RestController
public class VideoCaptureController {

  @GetMapping(value = "/capture",produces = MediaType.IMAGE_PNG_VALUE)
  public byte[] capture(@RequestParam("url") String url) {
    try {
      return startCapture(url);
    } catch (IOException e) {
      throw new RuntimeException(e);
    } catch (InterruptedException e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * 开始截图
   */
  public byte[] startCapture(String url) throws IOException, InterruptedException{
    FFmpegFrameGrabber grabber = FFmpegFrameGrabber.createDefault(url);
    grabber.setOption("rtsp_transport", "tcp"); // 使用tcp的方式，不然会丢包很严重
    //grabber.setImageWidth(960); //设置宽高尺寸（不设置则使用视频流原始宽高）
    //grabber.setImageHeight(540);
    System.out.println("--- grabber start ---");
    grabber.start();
    while (true){
      Frame frame = grabber.grabImage();
      if (frame != null) {
        //获取BufferedImage对象
        BufferedImage bufferedImage = frameToBufferedImage(frame);
        //将获取BufferedImage转成byte[]返回
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        ImageIO.write(bufferedImage, "png", out);
        grabber.stop();
        grabber.release();
        System.out.println("--- grabber end ---");
        return out.toByteArray();
      }
    }
  }

  /**
   * 创建BufferedImage对象
   */
  public BufferedImage frameToBufferedImage(Frame frame) {
    Java2DFrameConverter converter = new Java2DFrameConverter();
    BufferedImage bufferedImage = converter.getBufferedImage(frame);
    return bufferedImage;
  }
}

（2）运行效果如下：