使用java错误运行opencv

2024年1月31日 238次阅读

我已经开始使用JAVA语言学习OpenCV.我试图运行从中借来的非常简单的代码

http://docs.opencv.org/2.4.4-beta/doc/tutorials/introduction/desktop_java/java_dev_intro.html

并使用eclipse(JUNO).当我运行以下代码时

import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.MatOfRect;
import org.opencv.core.Point;
import org.opencv.core.Rect;
import org.opencv.core.Scalar;
import org.opencv.highgui.Highgui;
import org.opencv.objdetect.CascadeClassifier;

//
// Detects faces in an image, draws boxes around them, and writes the results
// to "faceDetection.png".
//
class DetectFaceDemo {
  public void run() {
    System.out.println("\nRunning DetectFaceDemo");

    // Create a face detector from the cascade file in the resources
    // directory.
    CascadeClassifier faceDetector = new CascadeClassifier(getClass().getResource("/lbpcascade_frontalface.xml").getPath());
    Mat image = Highgui.imread(getClass().getResource("/lena.png").getPath());

    // Detect faces in the image.
    // MatOfRect is a special container class for Rect.
    MatOfRect faceDetections = new MatOfRect();
    faceDetector.detectMultiScale(image, faceDetections);

    System.out.println(String.format("Detected %s faces", faceDetections.toArray().length));

    // Draw a bounding box around each face.
    for (Rect rect : faceDetections.toArray()) {
        Core.rectangle(image, new Point(rect.x, rect.y), new Point(rect.x + rect.width, rect.y + rect.height), new Scalar(0, 255, 0));
    }

    // Save the visualized detection.
    String filename = "faceDetection.png";
    System.out.println(String.format("Writing %s", filename));
    Highgui.imwrite(filename, image);
  }
}

public class HelloOpenCV {
  public static void main(String[] args) {
    System.out.println("Hello, OpenCV");

    // Load the native library.
    System.loadLibrary("opencv_java245");
    new DetectFaceDemo().run();
  }
}

我明白了

Hello, OpenCV

Running DetectFaceDemo
Exception in thread "main" java.lang.NullPointerException
    at DetectFaceDemo.run(HelloOpenCV.java:20)
    at HelloOpenCV.main(HelloOpenCV.java:48)

哪里
**

20     CascadeClassifier faceDetector = new CascadeClassifier(getClass().getResource("lbpcascade_frontalface.xml").getPath());
48    new DetectFaceDemo().run();

**

我是这个领域的新手,不知道如何克服这个错误.我需要你的帮助.

最佳答案 getClass().getResource()从类路径加载资源,如果找不到文件,它将返回null.所以在你的情况下似乎没有加载文件,当你调用getPath()时,你会得到空指针异常.您需要检查,无论您正在构建,xml文件都会被复制到编译类文件的位置.或者只是确保类路径中存在xml文件.

希望能帮助到你！

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