我正在尝试使用JavaCV实现一个简单的人脸识别代码。我有一个错误，但不知道为什么。

public static void recognise(Context context, File sampleDir, File testFile) {

    // DEBUG-1
    if(sampleDir!=null)
        log(context, "1. sampleDir OK. " + testFile.getAbsolutePath());
    else {
        log(context, "1. sampleDir is Null");
        return;
    }


    FilenameFilter pngFilter = new FilenameFilter() {
        public boolean accept(File dir, String name) {
            return name.toLowerCase().endsWith(".png");
        }
    };

    File[] imageFiles = sampleDir.listFiles(pngFilter);

    // DEBUG-2
    if(imageFiles!=null) {
        log(context, "2. ImageFile OK, Files :");
        for(File imageFile : imageFiles)
            log(context, "File : " + imageFile.getAbsolutePath() );
    }
    else {
        log(context, "2. ImageFile Array Null");
        return;
    }

    // DEBUG-.5
    if(testFile!=null)
        log(context, "2.5. testFile OK. " + testFile.getAbsolutePath());
    else {
        log(context, "2.5. testFile is Null");
        return;
    }

    IplImage testImage = cvLoadImage(testFile.getAbsolutePath());
    // DEBUG-3
    if(imageFiles!=null)
        log(context, "3. testImageIpl OK");
    else {
        log(context, "3. testImageIpl is Null");
        return;
    }

    MatVector images = new MatVector(imageFiles.length);

    int[] labels = new int[imageFiles.length];

    int counter = 0;
    int label;

    IplImage img;
    IplImage grayImg;

    for (File image : imageFiles) {
        // Get image and label:
        img = cvLoadImage(image.getAbsolutePath());
        label = Integer.parseInt(image.getName().split("\\-")[0]);

        // Convert image to gray scale:
        grayImg = IplImage.create(img.width(), img.height(), IPL_DEPTH_8U, 1);
        cvCvtColor(img, grayImg, CV_BGR2GRAY);
        // Append it in the image list:
        images.put(counter, grayImg);
        // And in the labels list:
        labels[counter] = label;
        // Increase counter for next image:
        counter++;
    }

    //FaceRecognizer faceRecognizer = createFisherFaceRecognizer();
    FaceRecognizer faceRecognizer = createEigenFaceRecognizer();
    // FaceRecognizer faceRecognizer = createLBPHFaceRecognizer();

    faceRecognizer.train(images, labels);

    // Load the test image:
    IplImage greyTestImage = IplImage.create(testImage.width(), testImage.height(), IPL_DEPTH_8U, 1);
    cvCvtColor(testImage, greyTestImage, CV_BGR2GRAY);

    // And get a prediction:
    //int predictedLabel = faceRecognizer.predict(greyTestImage);
    //System.out.println("Predicted label: " + predictedLabel);

    int[] imageLabels = new int[1];
    double[] confidences = new double[1];

    faceRecognizer.predict(greyTestImage, imageLabels, confidences);

    log(context, "Result : Label - " + imageLabels[0] + "  Conf - " + confidences[0]);


}