OpenCV--c++ 学习笔记

直方图方向投影

作用：在输入图像中寻找与模板图像最匹配的区域，即定位模板图像出现在输入图像的位置。

步骤：

1. 加载模板图像和待反向投影图像；
2. 加载图像颜色空间，gray/HSV；
3. 计算模板图像的直方图；
4. 将待方向投影和模板图像的直方图赋值给反向投影函数，得到投影结果。

   #include <opencv2/opencv.hpp>
   #include <iostream>
   #include <math.h>
   
   using namespace cv;
   using namespace std;
   
   void drawHist(Mat& hist, int type, string name) {
       int hist_w = 512;
       int hist_h = 400;
       int width = 2;
       Mat histImage = Mat::zeros(hist_h, hist_w, CV_8UC3);
       normalize(hist, hist, 255, 0, type, -1, Mat());  // normalize hist values between 0 and 1
       namedWindow(name, WINDOW_NORMAL);
       imshow(name, hist);
   }
   
   int main() {
       //加载图像
       Mat img = imread("D:/images/hamd3.jpg");
       Mat sub_img = imread("D:/images/hand1.jpg");
       resize(img, img, Size(img.cols / 3, img.rows / 3), 0, 0, INTER_LINEAR);
       resize(sub_img, sub_img, Size(sub_img.cols / 3, sub_img.rows / 3), 0, 0, INTER_LINEAR);
       //cvtColor(img, img, COLOR_BGR2GRAY);
       //cvtColor(sub_img, sub_img, COLOR_BGR2GRAY);
       Mat img_HSV, sub_HSV, hist;
       if (img.empty() || sub_img.empty()) {
           printf("could not load image...\n");
           return -1;
       }
   
       imshow("img", img);
       imshow("sub_img", sub_img);
       //转换色彩空间
       cvtColor(img, img_HSV, COLOR_BGR2HSV);
       cvtColor(sub_img, sub_HSV, COLOR_BGR2HSV);
       //计算模板图像直方图
       int h_bins = 32;
       int s_bins = 32;
       int histSize[] = { h_bins, s_bins };
       float h_ranges[] = { 0, 180 };
       float s_ranges[] = { 0, 256 };
       const float* ranges[] = { h_ranges, s_ranges };  // ranges should be an array of pointers
       int channels[] = { 0, 1 };  // the channels to be used for hist computation
   
       // Compute the histogram
       calcHist(&sub_HSV, 1, channels, Mat(), hist, 2, histSize, ranges, true, false);
       drawHist(hist, NORM_INF, "hist");
       //反向投影
       Mat backproj;
       // Perform backprojection
       calcBackProject(&img_HSV, 1, channels, hist, backproj, ranges, 1.0);
       imshow("反向投影后结果", backproj);  // Avoid using Chinese characters in window names
   
       waitKey(0);
       return 0;
   }
   

代码运行结果