c++ - cvCalcHist 和 calcHist 的区别

Question

我试图了解 cvCalcHist 之间的区别，openCV c 版本 和 calcHist 中计算图像直方图的方法>，openCV c++ version 中计算图像直方图的方法。

openCV c版本代码:

    // load the color image
    IplImage* im = cvLoadImage("2.png");

    // get the color histogram
    IplImage* im32f = cvCreateImage(cvGetSize(im), IPL_DEPTH_32F, 3);
    cvConvertScale(im, im32f);

    int histSize[] = {32, 32, 32};
    float rgbRange[] = {0, 256};
    float* ranges[] = {rgbRange, rgbRange, rgbRange};

    CvHistogram* hist = cvCreateHist(3, histSize, CV_HIST_ARRAY, ranges);
    IplImage* b = cvCreateImage(cvGetSize(im32f), IPL_DEPTH_32F, 1);
    IplImage* g = cvCreateImage(cvGetSize(im32f), IPL_DEPTH_32F, 1);
    IplImage* r = cvCreateImage(cvGetSize(im32f), IPL_DEPTH_32F, 1);

    cvSplit(im32f, b, g, r, NULL);
    IplImage* planes[] = {b, g, r};
    cvCalcHist(planes, hist);

    // find min and max values of histogram bins
    float minval, maxval;
    cvGetMinMaxHistValue(hist, &minval, &maxval);
    cout << "Min : " << minval << " / Max : " << maxval << endl;

    //OUTPUT: Min : 0 / Max : 177617 

openCV c++版本代码:

    const int channels[] = {0, 1, 2};
    const int histSize[] = {32, 32, 32};
    const float rgbRange[] = {0, 256};
    const float* ranges[] = {rgbRange, rgbRange, rgbRange};
    Mat im = imread("2.png",IMREAD_COLOR);
    MatND hist;
    Mat im32fc3, backpr32f(im.cols, im.rows, CV_32F), backpr8u(im.cols, im.rows, CV_8U), backprBw;
    im.convertTo(im32fc3, CV_32F);

    // compute histogram, scale it to 0-255 range and backproject
    calcHist( &im32fc3, 1, channels, Mat(), hist, 1, histSize, ranges, true, false);
    // find min and max values of histogram bins
    double minval, maxval;
    cv::minMaxIdx(hist, &minval, &maxval);
    cout << "Min : " << minval << " / Max : " << maxval << endl;

    //OUTPUT: Min : 455 / Max : 476732

正如您在上面代码部分的 //OUTPUT 注释中看到的，两段代码的值不同，我认为我应该得到相同的结果。知道发生了什么事吗？

Answer 1

由于您在 B、G、R 中创建 3D 直方图，您需要告诉 calcHist 正确的维数:3。所以基本上您需要更改:

calcHist( &im32fc3, 1, channels, Mat(), hist, 1, histSize, ranges, true, false);
//                                            ^
//                                       one dimension

为此具有正确的维度数:

calcHist( &im32fc3, 1, channels, Mat(), hist, 3, histSize, ranges, true, false);
//                                            ^
//                                       three dimensions