c++ - 如何使用 vector 设置 OpenCV3 calcHist() 的参数？

Question

我正在使用上面的代码从灰度图像计算直方图；它工作正常。

cv::Mat imgSrc = cv::imread("Image.jpg", cv::IMREAD_UNCHANGED);
cv::Mat histogram; //Array for the histogram
int channels[] = {0}; 
int binNumArray[] = {256}; 
float intensityRanges[] = { 0, 256 }; 
const float* ranges[] = { intensityRanges };
cv::calcHist( &imgSrc, 1, channels, cv::noArray(), histogram, 1,     binNumArray, ranges, true, false) ;    

在 Kaehler & Bradski 的书中，他们将此称为“老式的 C 风格数组”，他们说新风格将使用 STL vector 模板，计算直方图的图像数组是使用 cv::InputArrayOfArrays 给出。但是，如果我尝试通过以下方式替换 channel 数组:

std::vector channel {0};

给出编译错误。所以我的问题是:1. 如何使用 vector 定义“channels”、“binNumArray”、“intensityRanges”的数组？2. 如何使用 cv::InputArrayOfArrays 定义输入图像数组？

Answer 1

这个例子同时显示了 "old" approach和 "new" approach ，所以你可以体会到差异。它基于在 OpenCV documentation 中找到的示例.

"new" 方法只是一个方便的包装器，在内部调用“旧” 方法。

#include <opencv2\opencv.hpp>
#include <vector>
using namespace cv;
using namespace std;


int main()
{
    Mat3b src = imread("path_to_image");
    Mat3b hsv;
    cvtColor(src, hsv, CV_BGR2HSV);

    Mat hist;
    Mat hist2;
    {
        // Quantize the hue to 30 levels
        // and the saturation to 32 levels
        int hbins = 30, sbins = 32;
        int histSize[] = { hbins, sbins };
        // hue varies from 0 to 179, see cvtColor
        float hranges[] = { 0, 180 };
        // saturation varies from 0 (black-gray-white) to
        // 255 (pure spectrum color)
        float sranges[] = { 0, 256 };
        const float* ranges[] = { hranges, sranges };

        // we compute the histogram from the 0-th and 1-st channels
        int channels[] = { 0, 1 };
        calcHist(&hsv, 1, channels, Mat(), // do not use mask
            hist, 2, histSize, ranges,
            true, // the histogram is uniform
            false);
    }

    {
        // Quantize the hue to 30 levels
        // and the saturation to 32 levels
        vector<int> histSize = { 30, 32 };
        // hue varies from 0 to 179, see cvtColor
        // saturation varies from 0 (black-gray-white) to
        // 255 (pure spectrum color)
        vector<float> ranges = { 0, 180, 0, 256 };
        // we compute the histogram from the 0-th and 1-st channels
        vector<int> channels = { 0, 1 };

        vector<Mat> mats = { hsv };
        calcHist(mats, channels, Mat(), // do not use mask
            hist2, histSize, ranges,
            /*true, // the histogram is uniform, this is ALWAYS true*/
            false);
    }
    return 0;
}