// TODO FaceDetectEngine 初始化
cv::Mat image = cv::imread(test_file, cv::IMREAD_UNCHANGED);// 原始影象
cv::Mat gray;
cv::cvtColor(image, gray, cv::COLOR_BGR2GRAY);// 灰度圖

// 檢測出人臉框
std::vector<FaceInfo> face_info_list = FaceDetectEngine.detect(gray.data, gray.cols, gray.rows);
int face_num = face_info_list.size();
for (int i = 0; i < face_num; ++i)
{
       FaceInfo faceInfo = face_info_list[i];
       float sketch_face_info[5] = {
               faceInfo.x * 1.0f / gray.cols,
               faceInfo.y * 1.0f / gray.rows,
               faceInfo.width * 1.0f / gray.cols,
               faceInfo.height * 1.0f / gray.rows,
               faceInfo.rotation
       };
       cv::Mat face_key_pionts = FaceDetectEngine.detectKeyPoints(gray, sketch_face_info);

		cv::Point leftTopP;
        leftTopP.x = faceInfo.x;
        leftTopP.y = faceInfo.y;

        cv::Point rightBottomP;
        rightBottomP.x = faceInfo.x + faceInfo.width;
        rightBottomP.y = faceInfo.y + faceInfo.height;

        // 繪製人臉框，cvRectangle函式引數： 圖片， 左上角， 右下角， 顏色， 線條粗細， 線條型別，點型別
        cv::rectangle(image, leftTopP, rightBottomP, cv::Scalar(0, 0, 255), 1, 4, 0);

		// 繪製 68 點的人臉關鍵點
		for (int i = 0; i < face_key_pionts.rows; i+=2) {	
            for (int j = 0; j < face_key_pionts.cols; ++j) {
            
                cv::Point point;//特徵點，用以畫在影象中
                point.x = face_key_pionts.at<float>(i, j);//特徵點在影象中橫座標
                point.y = face_key_pionts.at<float>(i + 1, j);//特徵點在影象中縱座標
                cv::circle(image, point, 1, cv::Scalar(0, 255, 0), 2);//在影象中畫出特徵點，1是圓的半徑
            }
        }
}

// 儲存圖片
FILE * file = fopen(save_path, "wb");
fwrite(image.data, image.elemSize(), image.cols * image.rows, file);
fclose(file);

// TODO 釋放 FaceDetectEngine 
 

效果圖如下：