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 = 30;//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 -1;
    }
    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[]= {0,0};
    mixChannels(&hsv, 1, &hue, 1, ch, 1);
    mixChannels(&temp_hsv, 1, &temp_hue, 1, ch, 1);

    
    //创建Trackbar来输入bin的数目
    namedWindow(WINDOW_NAME,WINDOW_AUTOSIZE);
    createTrackbar("色调组距", WINDOW_NAME,&bin,180, on_BinChange);

    //进行一次初始化
    on_BinChange(0, 0);

    imshow(WINDOW_NAME, src); 
    
    waitKey(0);
    return 0;
}

void on_BinChange(int, void*)
{
    //参数准备
    MatND hist;
    int histSize = max(bin, 2);
    float hue_range[] = { 0,180 };//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, 1, 0, Mat(), hist, 1, &histSize, &ranges, true, false);
    normalize(hist, hist, 0, 255, NORM_MINMAX, -1, Mat());

    //计算反向投影
    MatND backproj;
    calcBackProject(&hue,1,0,hist,backproj,&ranges,1,true);

    imshow("反向投影图", backproj);

    //绘制直方图参数准备
    int w = 400, h = 400;
    int bin_w = cvRound((double)w/histSize);
    Mat histImg = Mat::zeros(w,h,CV_8UC3);

    //绘制直方图
    for(int i=0;i<bin;i++)
    {
        rectangle(histImg, Point(i*bin_w,h),Point((i+1)*bin_w,h-cvRound(hist.at<float>(i)*h/255.0)),Scalar(100,123,255),-1);
    }

    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。