OpenCV绘制带有轴标签和坐标的直方图

Question

我阅读了关于如何绘制直方图的OpenCV documentation，并且我已经根据我的需要调整了教程中的代码，因此输出是这样的条形直方图：

我正在寻找一种方法来添加带有标签和索引的轴。有没有任何无痛的解决方案来实现这一目标？

Answer 1

如果您仍然需要解决方案，并且不介意使用gnuplot。

这里有一个示例，我读取彩色图像，将其变为灰色，计算直方图，然后绘制直方图。

main.cpp

#include <iostream>
#include <vector>
#include <opencv2/opencv.hpp>

#include "gnuplot-iostream.h"

int main(int argc, char* argv[])
{
    cv::Mat image = cv::imread(argv[1], CV_LOAD_IMAGE_COLOR);
    if (!image.data)
    {
        LOGMSG_ERR_S_C() << "No image data\n";
        return -1;
    }
    cv::cvtColor(image, image, cv::COLOR_BGR2GRAY);

    // construct a grayscale histogram
    int binNumber = 256;
    int channels[] = {0};
    int numImages = 1;
    int histDim = 1;
    int histSize[] = {binNumber};
    float grayRange[] = {0, 256};
    const float* ranges[] = {grayRange};
    cv::MatND hist;
    cv::calcHist(&image, numImages, channels, cv::Mat(), hist, histDim, histSize, ranges);

    // plot the historgram
    std::vector<std::pair<double, double> > data;
    for (int bin = 0; bin < binNumber; bin++)
    {
        data.emplace_back(bin, hist.at<float>(bin));
    }
    Gnuplot gp;
    gp << "plot" << gp.file1d(data) << "with lines title 'hist'" << std::endl;
    cv::imshow("gray", image);

    // show the image and wait for a keypress
    cv::waitKey(0);
    cv::destroyAllWindows();

    return 0;
}

您可能需要对#include "gnuplot-iostream.h"使用升压

CMakeLists.txt

# Handle Boost
find_package(Boost COMPONENTS system iostreams filesystem REQUIRED) # gnuplot needed: system iostreams filesystem

include_directories(
  ${CMAKE_CURRENT_SOURCE_DIR}
  ${Boost_INCLUDE_DIR})

target_link_libraries(${targetName}
  ${Boost_LIBRARIES}
  ${OpenCV_LIBS})