OpenCV——反向投影（定位模板图像在输入图像中的位置）

反向投影：

 #include <opencv2/opencv.hpp>
 #include <iostream>

 using namespace cv;
 using namespace std;
 #define WINDOW_NAME "效果图"

 Mat src, hsv, hue;
 Mat temp, temp_hsv, temp_hue;
 int bin = ;//直方图组距
 void on_BinChange(int, void*);

 int main(int argc, char** argv)
 {
     src = imread("test.jpg");
     temp = imread("temp.jpg");
     if (src.empty()|| temp.empty()) {
         printf("Could not load image...");
         return -;
     }
     imshow("Input Image",src);

     //转到HSV空间
     cvtColor(src, hsv, COLOR_BGR2HSV);
     cvtColor(temp, temp_hsv, COLOR_BGR2HSV);

     //分离Hue色调通道
     hue.create(hsv.size(),hsv.depth());
     temp_hue.create(temp_hsv.size(), temp_hsv.depth());
     int ch[]= {,};
     mixChannels(&hsv, , &hue, , ch, );
     mixChannels(&temp_hsv, , &temp_hue, , ch, );

     //创建Trackbar来输入bin的数目
     namedWindow(WINDOW_NAME,WINDOW_AUTOSIZE);
     createTrackbar("色调组距", WINDOW_NAME,&bin,, on_BinChange);

     //进行一次初始化
     on_BinChange(, );

     imshow(WINDOW_NAME, src); 

     waitKey();
     return ;
 }

 void on_BinChange(int, void*)
 {
     //参数准备
     MatND hist;
     int histSize = max(bin, );
     float hue_range[] = { , };//h通道的取值范围
     const float* ranges = {hue_range};

     //计算直方图并归一化
     //calcHist(&hue, 1, 0, Mat(), hist, 1, &histSize, &ranges, true, false);
     //normalize(hist,hist,0,255,NORM_MINMAX,-1,Mat());
     calcHist(&temp_hue, , , Mat(), hist, , &histSize, &ranges, true, false);
     normalize(hist, hist, , , NORM_MINMAX, -, Mat());

     //计算反向投影
     MatND backproj;
     calcBackProject(&hue,,,hist,backproj,&ranges,,true);

     imshow("反向投影图", backproj);

     //绘制直方图参数准备
     int w = , h = ;
     int bin_w = cvRound((double)w/histSize);
     Mat histImg = Mat::zeros(w,h,CV_8UC3);

     //绘制直方图
     for(int i=;i<bin;i++)
     {
         rectangle(histImg, Point(i*bin_w,h),Point((i+)*bin_w,h-cvRound(hist.at<float>(i)*h/255.0)),Scalar(,,),-);
     }

     imshow("直方图",histImg);

 }

直方图反向投影可以在“输入图像”中 找到和“模板”直方图特征相似的部分。