OpenCV 错误：Java 和 opencv 3.0 中的断言失败 (!empty())，这是什么意思？

Question

我正在尝试在 java 中运行代码，当我运行此代码时，它会引发以下错误：

OpenCV Error: Assertion failed (!empty()) in cv::CascadeClassifier::detectMultiScale, file C:\builds\master_PackSlaveAddon-win64-vc12-static\opencv\modules\objdetect\src\cascadedetect.cpp, line 1634
Exception in thread "main" CvException [org.opencv.core.CvException: cv::Exception: C:\builds\master_PackSlaveAddon-win64-vc12-static\opencv\modules\objdetect\src\cascadedetect.cpp:1634: error: (-215) !empty() in function cv::CascadeClassifier::detectMultiScale
]
    at org.opencv.objdetect.CascadeClassifier.detectMultiScale_1(Native Method)
    at org.opencv.objdetect.CascadeClassifier.detectMultiScale(CascadeClassifier.java:103)
    at FaceDetector.main(FaceDetector.java:30)

我的源代码如下：

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.objdetect.CascadeClassifier;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;

public class FaceDetector {

    public static void main(String[] args) {

        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
        System.out.println("\nRunning FaceDetector");

       CascadeClassifier faceDetector = new CascadeClassifier(FaceDetector.class.getResource("haarcascade_frontalface_alt.xml").getPath());
        //CascadeClassifier cascade1 = new CascadeClassifier("C:/OpenCV/opencv/sources/data/haarcascades/haarcascade_frontalface_alt.xml");
        //CascadeClassifier cascade1 = new CascadeClassifier("C:/OpenCV/opencv/sources/data/lbpcascade/lbpcascade_frontalface.xml");
        //CascadeClassifier cascade1=new CascadeClassifier();
        //cascade1.load("C:/opencv2.4.9/sources/data/haarcascades/haarcascade_frontalface_alt.xml");
       faceDetector.load("C:/opencv2.4.9/sources/data/haarcascades/haarcascade_frontalface_alt.xml");
        System.out.println("step1");
        Mat image = Imgcodecs.imread(FaceDetector.class.getResource("anuj.jpg").getPath());
        System.out.println("step2");
        MatOfRect faceDetections = new MatOfRect();
        System.out.println("step3");
        faceDetector.detectMultiScale(image, faceDetections);
        System.out.println("step4");
        try {
            System.out.println(String.format("Detected %s faces", faceDetections.toArray().length));
        } catch (Exception e) {
            // TODO Auto-generated catch block
            System.err.println("ERROR IS HERE");
            //e.printStackTrace();
        }

        for (Rect rect : faceDetections.toArray()) {
            Imgproc.rectangle(image, new Point(rect.x, rect.y), new Point(rect.x + rect.width, rect.y + rect.height),
                    new Scalar(0, 255, 0));
        }

        String filename = "ouput.png";
        System.out.println(String.format("Writing %s", filename));
        Imgcodecs.imwrite(filename, image);
    }
}

请告诉我我的错误是什么。我无法解决这个问题。我还尝试了代码的许多变体，但它不起作用。

Answer 1

似乎没有从文件中正确加载分类器。

请确保 faceDetector.load() 返回 true，否则不会读取文件。

Answer 2

这是 5 个月前发布的，但为了那些在尝试了所有建议的解决方案后仍将面临这一挑战的人，我在面临同样的挑战后发现了另一种可能性。如果getPath()返回的URL中有空格，则空格返回为"%20"。

例如： /C:/Users/Ayomide.Johnson/Documents/NetBeansProjects/OpenCV%20Test%20Project/build/classes/haarcascade_frontalface_alt.xml
您需要将"%20" 改回空格。

我的一周是： FaceDetector.class.getResource("x.JPG").getPath().substring(1).replace("%20", " ") 成功了！

注意：substring(1) 是去掉路径中最初的"/"。如果您不需要该调用，可以将其删除。

Answer 3

我也在努力解决同样的问题。指示 haarcascade_frontalface_alt.xml 文件的目录对我来说效果很好。你也可以试试。

package faceDetection;

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.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;
import org.opencv.objdetect.CascadeClassifier;

public class FaceDetection
{

    public static void main(String[] args)
    {

        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);


        CascadeClassifier faceDetector = new CascadeClassifier();
        faceDetector.load("D:\\OpenCv\\opencv\\sources\\data\\haarcascades\\haarcascade_frontalface_alt.xml");
        System.out.println ( "Working" );
        // Input image
        Mat image = Imgcodecs.imread("E:\\input.jpg");

        // Detecting faces
        MatOfRect faceDetections = new MatOfRect();
        faceDetector.detectMultiScale(image, faceDetections);

        // Creating a rectangular box showing faces detected
        for (Rect rect : faceDetections.toArray())
        {
            Imgproc.rectangle(image, new Point(rect.x, rect.y),
             new Point(rect.x + rect.width, rect.y + rect.height),
                                           new Scalar(0, 255, 0));
        }

        // Saving the output image
        String filename = "Ouput.jpg";
        Imgcodecs.imwrite("E:\\"+filename, image);
    }
}

Answer 4

"C:\\opencv2.4.9\\sources\\data\\haarcascades\\haarcascade_frontalface_alt.xml"

在窗口中给出路径时使用双斜杠。

Answer 5

将 convert-buffered-image 添加到 mat 类型变量可以解决问题。

package facedetect;

import java.awt.image.BufferedImage;
import java.awt.image.DataBufferByte;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

import org.opencv.core.Core;
import org.opencv.core.CvType;
import org.opencv.core.Mat;
import org.opencv.core.MatOfRect;
import org.opencv.core.Rect;
import org.opencv.objdetect.CascadeClassifier;

public class FaceDetector {
    // https://blog.openshift.com/day-12-opencv-face-detection-for-java-developers/
    // make user library and add it to project

    public static void main(String[] args) throws IOException {
        BufferedImage image = ImageIO.read(new File("/hayanchoi/scene1.png"));
        detectFace(image);
    }

    private static Mat convertBufImg2Mat(BufferedImage image) {
        DataBufferByte s;
        byte[] data = ((DataBufferByte) image.getRaster().getDataBuffer()).getData();
        Mat mat = new Mat(image.getHeight(), image.getWidth(), CvType.CV_8UC3);
        mat.put(0, 0, data);
        return mat;
    }

    private static int detectFace(BufferedImage image) {

        System.out.println("step0: Running FaceDetector");
        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
        CascadeClassifier faceDetector = new CascadeClassifier(
                FaceDetector.class.getResource("haarcascade_frontalface_alt.xml").getPath());
        if (!faceDetector.load("E:/hayanchoi/FaceDetectionTest/bin/facedetect/haarcascade_frontalface_alt.xml")) {
            return -1;
        }

        System.out.println("step1: convert bufferedimage to mat type");
        Mat matImage = convertBufImg2Mat(image);


        System.out.print("step2: detect face- ");
        MatOfRect faceDetections = new MatOfRect();
        faceDetector.detectMultiScale(matImage, faceDetections);
        System.out.println(String.format(" %s faces", faceDetections.toArray().length));

        System.out.println("step3: write faces");
        String filename = "/0_research/" + "ouput.png";
        for (Rect rect : faceDetections.toArray()) {
            writeFrame(filename, matImage, rect);
        }
        return faceDetections.toArray().length;
    }

    private static BufferedImage cropImage(BufferedImage src, Rect rect) {
        BufferedImage dest = src.getSubimage(rect.x, rect.y, rect.width, rect.height);
        return dest;
    }

    public static void writeFrame(String filename, Mat mat, Rect rect) {

        byte[] data = new byte[mat.rows() * mat.cols() * (int) (mat.elemSize())];
        mat.get(0, 0, data);
        if (mat.channels() == 3) {
            for (int i = 0; i < data.length; i += 3) {
                byte temp = data[i];
                data[i] = data[i + 2];
                data[i + 2] = temp;
            }
        }
        BufferedImage image = new BufferedImage(mat.cols(), mat.rows(), BufferedImage.TYPE_3BYTE_BGR);
        image.getRaster().setDataElements(0, 0, mat.cols(), mat.rows(), data);
        BufferedImage frame = cropImage(image, rect);
        try {
            ImageIO.write(frame, "png", new File(filename + ".png"));

        } catch (IOException e) {
            e.printStackTrace();
        } 

    }


} 

Answer 6

Java 不适用于 getResoure("...").getPath() 因此，将所有具有该功能的行更改为绝对路径，例如："C:/Users/USER/workspace/SmallTest/bin/face.jpg" 我刚刚解决了。 对不起英语不好

Answer 7

首先，在这种情况下，您应该检查CascadeClassifier 是否正确加载了指定的 XML 资源。 有两种方法可以做到这一点：要么检查load() 方法是否返回true。另一种方法（例如，如果您没有使用此方法，只需在构造函数中指定必要的资源）是使用 empty() 方法来确保分类器已正确加载。