I am trying to detect the mouth in an image with openCV, so I am using the following code:
#include "face_detection.h"
using namespace cv;
// Function detectAndDisplay
void detectAndDisplay(const std::string& file_name, cv::CascadeClassifier& face_cascade, cv::CascadeClassifier& mouth_cascade)
{
Mat frame = imread(file_name);
std::vector<Rect> faces;
Mat frame_gray;
Mat crop;
Mat res;
Mat gray;
cvtColor(frame, frame_gray, COLOR_BGR2GRAY);
equalizeHist(frame_gray, frame_gray);
// Detect faces
face_cascade.detectMultiScale(frame_gray, faces, 1.1, 3, 0 | CASCADE_SCALE_IMAGE, Size(30, 30));
for(unsigned int i=0;i<faces.size();i++)
{
rectangle(frame,faces[i],Scalar(255,0,0),1,8,0);
Mat face = frame(faces[i]);
cvtColor(face,face,CV_BGR2GRAY);
std::vector <Rect> mouthi;
mouth_cascade.detectMultiScale(face, mouthi);
for(unsigned int k=0;k<mouthi.size();k++)
{
Point pt1(mouthi[k].x+faces[i].x , mouthi[k].y+faces[i].y);
Point pt2(pt1.x+mouthi[k].width, pt1.y+mouthi[k].height);
rectangle(frame, pt1,pt2,Scalar(0,255,0),1,8,0);
}
}
imshow("Frame", frame);
waitKey(33);
}
The classifiers are haarcascade_frontalface_alt.xml
and haarcascade_mcs_mouth.xml
.
The face is detected correctly but the mouth is not: I also obtain the eyes and some other parts, like the forehead. Is there a way to detect only the mouth?
I think I managed to solve the problem: focusing on the lower half of the face and increasing the scale factor did the trick and now I am able to detect the mouth with a good precision. Anyway this task seems much more complicated than face detection, even if I am using "simple" images, which means straight and full frontal.
Here are two examples: a success and a failure.