OpenCV访问MAT对象中的RGB值

OpenCV Access RGB values in a MAT object

本文关键字：RGB 对象 访问 MAT OpenCV      更新时间：2023-10-16

我正试图使用OpenCV从网络摄像头获取帧，并将其转换为HSV（色调、饱和度、值）Mat对象并设置阈值。

当我打印阈值图像像素值时，它为所有像素提供[0,0,0]，即使是黑色像素值也是[0,0,0]。如果选择的像素是黑色的，我需要做一些计算；如何访问像素值？。

    imgOriginal=frame from camera 

    Mat imgHSV;
    cvtColor(imgOriginal, imgHSV, COLOR_BGR2HSV); //Convert the captured frame from BGR to HSV
    Mat imgThresholded;
    inRange(imgHSV, Scalar(iLowH, iLowS, iLowV), Scalar(iHighH, iHighS, iHighV), imgThresholded); //Threshold the image
    //morphological opening (remove small objects from the foreground)
    erode(imgThresholded, imgThresholded, getStructuringElement(MORPH_ELLIPSE, Size(5, 5)) );
    dilate( imgThresholded, imgThresholded, getStructuringElement(MORPH_ELLIPSE, Size(5, 5)) ); 
    //morphological closing (fill small holes in the foreground)
    dilate( imgThresholded, imgThresholded, getStructuringElement(MORPH_ELLIPSE, Size(5, 5)) ); 
    erode(imgThresholded, imgThresholded, getStructuringElement(MORPH_ELLIPSE, Size(5, 5)) );

    //************************************

    std::vector<cv::Vec3b> pixels(imgThresholded.rows * imgThresholded.cols);
    cv::Mat m(imgThresholded.rows, imgThresholded.cols, CV_8UC3, &pixels[0]);
    imgThresholded.copyTo(m);

    for(int i =0;i<1000;i++)
    cout<<pixels[0];
    if(pixels[0][0]==black)
    // do some calculations!

for(int i =0;i<1000;i++)
    cout<<pixels[0];

将只打印第一个像素1000次。我想你的意思是：

Vec3b black(0, 0, 0);
for(int i =0;i<1000;i++)
{
    cout << pixels[i];
    if pixels[i] == black)
    {
       /* ... */
    }
}

但是，为什么要麻烦将像素复制到std:：向量中呢？你可以做这个

Vec3b black(0, 0, 0);
Mat img(imgThresholded); // just to make a short name
for(int y = 0; y < img.rows; ++y)
{
    Vec3b* row = img.ptr<Vec3b>(y);
    for(int x = 0; x < img.cols; ++x)
    {
        Vec3b& pixel = row[x];
        if(pixel == black)
        {
            /* ... */
        }
    }
 }
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