c++ - 使用 open cv 和 c++ 检测和计算图像上的人脸

Question

虽然我是初学者，但我正在使用 opencv 和 C++。我正在尝试使用 Haarcascade 从一组图像中检测和计数人脸。我只想得到每张图片上的人脸数量。我如何编辑此代码以获取图像上的面孔数量？？？？

// Function detectAndDisplay
void detectAndDisplay(Mat frame)
{
std::vector<Rect> faces;
Mat frame_gray;
Mat crop;
Mat res;
Mat gray;
string text;
stringstream sstm;

cvtColor(frame, frame_gray, COLOR_BGR2GRAY);
equalizeHist(frame_gray, frame_gray);

// Detect faces
face_cascade.detectMultiScale(frame_gray, faces, 1.1, 2, 0 |     CASCADE_SCALE_IMAGE, Size(30, 30));

// Set Region of Interest
cv::Rect roi_b;
cv::Rect roi_c;

size_t ic = 0; // ic is index of current element
int ac = 0; // ac is area of current element

size_t ib = 0; // ib is index of biggest element
int ab = 0; // ab is area of biggest element

for (ic = 0; ic < faces.size(); ic++) // Iterate through all current  elements (detected faces)

{
    roi_c.x = faces[ic].x;
    roi_c.y = faces[ic].y;
    roi_c.width = (faces[ic].width);
    roi_c.height = (faces[ic].height);

    ac = roi_c.width * roi_c.height; // Get the area of current element (detected face)

    roi_b.x = faces[ib].x;
    roi_b.y = faces[ib].y;
    roi_b.width = (faces[ib].width);
    roi_b.height = (faces[ib].height);

    ab = roi_b.width * roi_b.height; // Get the area of biggest element, at beginning it is same as "current" element

    if (ac > ab)
    {
        ib = ic;
        roi_b.x = faces[ib].x;
        roi_b.y = faces[ib].y;
        roi_b.width = (faces[ib].width);
        roi_b.height = (faces[ib].height);
    }

    crop = frame(roi_b);
    resize(crop, res, Size(128, 128), 0, 0, INTER_LINEAR); // This will be needed later while saving images
    cvtColor(crop, gray, CV_BGR2GRAY); // Convert cropped image to Grayscale

    // Form a filename
    filename = "";
    stringstream ssfn;
    ssfn << filenumber << ".png";
    filename = ssfn.str();
    filenumber++;

    imwrite(filename, gray);
    printf("filename");
    Point pt1(faces[ic].x, faces[ic].y); // Display detected faces on main window - live stream from camera
    Point pt2((faces[ic].x + faces[ic].height), (faces[ic].y + faces[ic].width));
    rectangle(frame, pt1, pt2, Scalar(0, 255, 0), 2, 8, 0);
}

// Show image
/*sstm << "Crop area size: " << roi_b.width << "x" << roi_b.height << " Filename: " << filename;
text = sstm.str();

putText(frame, text, cvPoint(30, 30), FONT_HERSHEY_COMPLEX_SMALL, 0.8, cvScalar(0, 0, 255), 1, CV_AA);
imshow("original", frame);

if (!crop.empty())
{
    imshow("detected", crop);
}
else
    destroyWindow("detected");*/

Answer 1

修改了您发布的代码示例以仅返回图像中检测到的人脸数量...

// Function to count the detected faces in your image
void countFacesInImage(Mat frame)
{
    std::vector<Rect> faces;
    Mat frame_gray;

    cvtColor(frame, frame_gray, COLOR_BGR2GRAY);
    equalizeHist(frame_gray, frame_gray);

    // Detect faces
    face_cascade.detectMultiScale(frame_gray, faces, 1.1, 2, 0 |     CASCADE_SCALE_IMAGE, Size(30, 30));

    return faces.size();
}

如果您想知道哪些人脸被检测到，哪些人没有被检测到，您可以在返回之前添加此代码:

cv::Mat tmpImage = frame.clone();
for(unsigned int i=0; i<faces.size(); ++i)
{
    cv::rectangle(tmpImage, faces[i], cv::Scalar(0,255,0), 2);
}
cv::imshow("faces", tmpImage);
cv::waitKey(0);

在每张图像之后，您必须按下带有事件窗口“面孔”的键。您可以更改为 cv::waitKey(n) 等待 n 毫秒，而无需按键。