Opencv：将bgr图片转换成Lab、gray空间

本文链接： https://blog.csdn.net/Teddygogogo/article/details/84932648

刚开始入门Opencv，无意间发现书本上有对rgb空间进行转换，我就查阅了一些资料，拓展到Lab的空间。

还有一种简单粗暴的读像素点rgb、gray、Lab通道信息的方法，img.at<uchar>(y,x)。

需要注意的是图像在opencv的存储顺序是bgr而不是rgb，同时lab的标准转换最后需要进行映射。

#include <opencv2/opencv.hpp>

//向编译器说明你所调用的函数处于cv、std命名空间
using namespace cv;
using namespace std;

int main()
{
   cv::Mat img_rgb, img_rgb1, img_gray, img_lab, img_canny;
   namedWindow("Window1", cv::WINDOW_AUTOSIZE);
   namedWindow("Window2", cv::WINDOW_AUTOSIZE);
   namedWindow("Window3", cv::WINDOW_AUTOSIZE);
   namedWindow("Window4", cv::WINDOW_AUTOSIZE);
   namedWindow("Window5", cv::WINDOW_AUTOSIZE);

   img_rgb = imread("D:/Desktop/pic/色卡RGBCMYK.tif", -1);
   if (img_rgb.empty()) return -1;
   cv::imshow("Window1", img_rgb);
   //读取像素点(y,x)的bgr值
   //读取第一个像素点(0,0)的b值
   std::cout << "b thers is :" << (unsigned int)img_rgb.at<uchar>(0, 0) << std::endl;
   //读取第一个像素点(0,1)的g值
   std::cout << "g thers is :" << (unsigned int)img_rgb.at<uchar>(0, 1) << std::endl;
   //读取第一个像素点(0,2)的r值
   std::cout << "r thers is :" << (unsigned int)img_rgb.at<uchar>(0, 2) << std::endl << std::endl;

   cv::cvtColor(img_rgb, img_gray, cv::COLOR_BGR2GRAY);
   cv::imshow("Window2", img_gray);
   //读取第一行第一列像素点的灰度值
   std::cout << "gray1 thers is :" << (unsigned int)img_gray.at<uchar>(0, 0) << std::endl;
   //读取第一行第二列像素点的灰度值
   std::cout << "gray2 thers is :" << (unsigned int)img_gray.at<uchar>(0, 1) << std::endl << std::endl;

   cv::cvtColor(img_rgb, img_lab, cv::COLOR_BGR2Lab);
   cv::imshow("Window3", img_lab);
   //读取第一个像素点(0,0)的l值，需要进行映射，实际的范围是[0,255]，理论l的范围是[0,100]
   std::cout << "l thers is :" << (int)(img_lab.at<uchar>(0, 0) * 100 / 255) << std::endl;
   //读取第一个像素点(0,1)的a值，需要进行映射，实际的范围是[0,255]，理论a的范围是[-128,127]
   std::cout << "a thers is :" << (int)img_lab.at<uchar>(0, 1) - 128 << std::endl;
   //读取第一个像素点(0,2)的b值，需要进行映射，实际的范围是[0,255]，理论b的范围是[-128,127]
   std::cout << "b thers is :" << (int)img_lab.at<uchar>(0, 2) - 128 << std::endl << std::endl;

   cv::cvtColor(img_lab, img_rgb1, cv::COLOR_Lab2BGR);
   cv::imshow("Window4", img_rgb1);
   //读取第一个像素点(0,0)的l值
   std::cout << "b1 thers is :" << (int)img_rgb1.at<uchar>(0, 300) << std::endl;
   //读取第一个像素点(0,1)的a值
   std::cout << "g1 thers is :" << (int)img_rgb1.at<uchar>(0, 301) << std::endl;
   //读取第一个像素点(0,2)的b值
   std::cout << "r1 thers is :" << (int)img_rgb1.at<uchar>(0, 302) << std::endl << std::endl;

   cv::Canny(img_gray, img_canny, 10, 100, 3, true);
   cv::imshow("Window5", img_canny);
   std::cout << "pixel thers is :" << (unsigned int)img_canny.at<uchar>(0, 0) << std::endl;
   std::cout << "pixel thers is :" << (unsigned int)img_canny.at<uchar>(0, 1) << std::endl;
   std::cout << "pixel thers is :" << (unsigned int)img_canny.at<uchar>(0, 2) << std::endl;

   waitKey(0);
   destroyWindow("Window1");
   destroyWindow("Window2");
   destroyWindow("Window3");
   destroyWindow("Window4");
   destroyWindow("Window5");
}

Opencv：将bgr图片转换成Lab、gray空间

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