ROI

2020-12-20
ROI(region of interest)也就是感兴趣区域。也就是图像的一部分。OpenCV使用rect可以提取出来图像的ROI。当然也可以利用鼠标左右键选择自己感兴趣的区域。
示例代码：
#include <iostream>
#include <string>
#include <cmath>
#include <opencv2/opencv.hpp>
using std::sin;
using std::cos;
using std::abs;
using std::min;
//使用CommandLineParser对输入的参数进行分析，获取输入的图片路径
std::string GetFileName(int argc,char* argv[])
{
    /*
    argc : the size of argv[]
    argv : the parameters of comdline
    */
    const char* key = {
    "{help h usage? || usage information}"
    "{@picture || input picture}"
    };
     cv::CommandLineParser parser(argc,argv,key);
    if (parser.has("help"))
    {
        parser.printMessage();
        exit(0);
    }
    //如果没有输入图片路径
    if (!parser.check())
    {
        parser.printErrors();
        exit(-1);
    }
    std::string fileName = parser.get<std::string>(0);
    return fileName;
}
cv::Point startPoint;
cv::Point endPoint;
bool downFlag = false;
bool upFlag = false;
void SetRoi(int event,int x,int y,int flags,void* userdata)
{
    cv::Mat srcImage = *(cv::Mat*)userdata;
    if (event == CV_EVENT_LBUTTONDOWN)
    {
        downFlag = true;
        startPoint.x = x;
        startPoint.y = y;
    }
    if (event == CV_EVENT_LBUTTONUP)
    {
        upFlag = true;
        endPoint.x = x;
        endPoint.y = y;
        cv::Mat tempImage = srcImage.clone();
         cv::rectangle(tempImage,startPoint,endPoint,cv::Scalar(255,0,0),2,cv::LINE_8,0);
         cv::imshow("srcImage",tempImage);
    }
    if (downFlag && upFlag)
    {
        cv::Rect rect;
        rect.width = abs(startPoint.x - endPoint.x);
        rect.height = abs(startPoint.y - endPoint.y);
        rect.x = min(startPoint.x,endPoint.x);
        rect.y = min(startPoint.y,startPoint.y);

        cv::Mat roiImage(srcImage,rect);

        cv::imshow("Roi",roiImage);
        downFlag = false;
        upFlag = false;
    }
    cv::waitKey(0);
}
int main(int argc,char *argv[])
{
    std::string ImageFilePath = GetFileName(argc,argv);
    cv::Mat srcImage = cv::imread(ImageFilePath);
    if (srcImage.empty())
    {
        std::cerr << "fail to load image" <<std::endl;
        exit(-1);
    }
    cv::namedWindow("srcImage");
    cv::imshow("srcImage",srcImage);
    cv::setMouseCallback("srcImage",SetRoi,(void*)&srcImage);
    cv::waitKey(0);
    cv::destroyAllWindows();
    return 0;
}