从摄像头中检测脸并保存图像

改写自：http://docs.opencv.org/doc/tutorials/objdetect/cascade_classifier/cascade_classifier.html

 #include "opencv2/objdetect/objdetect.hpp"
 #include "opencv2/highgui/highgui.hpp"
 #include "opencv2/imgproc/imgproc.hpp"

 #include <iostream>
 #include <stdio.h>

 using namespace std;
 using namespace cv;

 /** Function Headers */
 void detectAndDisplay( Mat frame );

 /** Global variables */
 String face_cascade_name = "haarcascade_frontalface_alt.xml";
 CascadeClassifier face_cascade;
 string window_name = "Capture - Face detection";

 /** @function main */
 int main( int argc, const char** argv )
 {
   CvCapture* capture;
   Mat frame;

   //-- 1. Load the cascades
   if( !face_cascade.load( face_cascade_name ) ){ printf("--(!)Error loading\n"); return -1; };

   //-- 2. Read the video stream
   capture = cvCaptureFromCAM( -1 );
   if( capture )
   {
     while( true )
     {
   frame = cvQueryFrame( capture );

   //-- 3. Apply the classifier to the frame
       if( !frame.empty() )
       { 
		   detectAndDisplay( frame ); 
	   }
       else
       { printf(" --(!) No captured frame -- Break!"); break; }

       int c = waitKey(10);
       if( (char)c == 'c' ) { 
		   break; 
	   }
      }
   }
   return 0;
 }

/** @function detectAndDisplay */
void detectAndDisplay( Mat frame )
{
  static int index = 0;
  char image_name[256];

  std::vector<Rect> faces;
  Mat frame_gray;

  cvtColor( frame, frame_gray, CV_BGR2GRAY );
  equalizeHist( frame_gray, frame_gray );

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

  for( size_t i = 0; i < faces.size(); i++ )
  {
    Point center( faces[i].x + faces[i].width*0.5, faces[i].y + faces[i].height*0.5 );
	rectangle(frame, faces[i], CV_RGB(0, 255,0), 1);
	Mat faceROI = frame_gray( faces[i] );
	sprintf(image_name, "frame%d_%d.jpg", index++, i);
	if(index <= 32){
		imwrite(image_name, faceROI);
		printf("frame %d write\n", index);
	}
  }
  //-- Show what you got
  imshow( window_name, frame );
 }