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。