OpenCV：23.实时人脸检测和识别

具体代码请看：NDKPractice项目的opencv71

1. 训练人脸样本

三种训练方法：

• eigenFace 算法 : EigenFaceRecognizer
• FisherFace 算法：FisherFaceRecognizer
• LBPH 算法：LBPHFaceRecognizer

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Java_com_east_opencv71_FaceDetection_trainingPattern(JNIEnv *env, jobject instance) {
    // 训练样本，这一步是在数据采集做的
    // train it
    vector<Mat> faces;
    vector<int> labels;

    // 样本比较少
    for (int i = 1; i <= 5; ++i) {
        for (int j = 1; j <= 5; ++j) {
            Mat face = imread(format("/storage/emulated/0/s%d/%d.pgm", i, j), 0);
            if (face.empty()) {
                LOGE("face mat is empty");
                continue;
            }
            // 确保大小一致
            resize(face, face, Size(128, 128));
            faces.push_back(face);
            labels.push_back(i);
        }
    }

    for (int i = 1; i <= 8; ++i) {
        Mat face = imread(format("/storage/emulated/0/face_%d.png", i), 0);
        if (face.empty()) {
            LOGE("face mat is empty");
            continue;
        }
        resize(face, face, Size(128, 128));
        faces.push_back(face);
        labels.push_back(11);
    }

    // 训练方法
    Ptr<BasicFaceRecognizer> model = EigenFaceRecognizer::create();
    // 采集了八张，同一个人 label 一样
    model->train(faces, labels);
    // 训练样本是 xml ，本地
    model->save("/storage/emulated/0/face_darren_pattern.xml");// 存的是处理的特征数据
    LOGE("樣本訓練成功");
}

2. 识别人脸

Java_com_east_opencv71_FaceDetection_loadPattern(JNIEnv *env, jobject instance,
                                                    jstring patternPath_) {
    const char *patternPath = env->GetStringUTFChars(patternPath_, 0);
    // 加载样本数据，Error:(142, 12) error: no matching member function for call to 'load' 怎么搞？
    // model->load(patternPath);
    FileStorage fs(patternPath, FileStorage::READ);
    // 报错，没有提示
    // CV_Assert(fs.isOpened());
    // 抛个 java 异常
    FileNode fn = fs.getFirstTopLevelNode();
    model->read(fn);
    env->ReleaseStringUTFChars(patternPath_, patternPath);
    LOGE("训练样本加载成功");
}