阈值的不同值 - 将 Matlab 代码转换为 OpenCV 代码

Question

我想要一些关于将 matlab 中的代码传递给 opencv c ++ 的帮助。我正在尝试对 RGB 通道进行一些操作，但是 thresh 的值不一样 - 我正在发送相同的图像。有人可以帮我吗？

MATLAB

im = imread('1.png');

[m,n,p] = size(im);

R=im(:, :, 1);
G=im(:, :, 2);
B=im(:, :, 3);

thresh=0;

for j=1:n
    for i=1:m
        thresh = thresh + double((1.262*G(i,j))-(0.884*R(i,j))-(0.311*B(i,j)));
    end
end

C++

#include <opencv2/opencv.hpp>
#include "opencv2/highgui.hpp"
#include <opencv2/core/mat.hpp>
#include <iostream>
using namespace std;
using namespace cv;


int main(){
    Mat img = imread("1.png", IMREAD_COLOR); 
    int thresh = 0;

    for(int j = 0; j <= img.cols; j++){
        for(int i = 0; i <= img.rows; i++){
            Vec3b color = img.at<Vec3b>(i,j);
            uchar a = color.val[0], b = color.val[1], c = color.val[2];
            thresh += double((1.262*b)-(0.884*c)-(0.311*a));
        }
    }
    
    cout << thresh;
    return 0;
}

Answer 1

第一个错误在于 for 循环的上限值，因为您超出了图像边框的范围。

j <= img.cols 应该是 j < img.cols 和

i <= img.rows 应该是i < img.rows

第二个错误是您没有为您的uchar 类型像素值进行显式类型转换

thresh += double((1.262*b)-(0.884*c)-(0.311*a));

应该是

thresh += double((1.262*static_cast<double>(b))
          -(0.884*static_cast<double>(c))
          -(0.311*static_cast<double>(a)));

这是我尝试过的全部代码：

#include <opencv2/opencv.hpp>
#include "opencv2/highgui.hpp"
#include <opencv2/core/mat.hpp>
#include <iostream>

using namespace std;
using namespace cv;


int main()
{
    Mat img = imread("img.jpg", IMREAD_COLOR);
    double thresh = 0.0;

    resize(img,img,Size(100,100));

    for(int j = 0; j < img.cols; j++){
        for(int i = 0; i < img.rows; i++){
            
            
            // 1ST WAY 
            Vec3b color = img.at<Vec3b>(i,j);
            uchar a = color.val[0], b = color.val[1], c = color.val[2];

            thresh += double((1.262*static_cast<double>(b))
                             -(0.884*static_cast<double>(c))
                             -(0.311*static_cast<double>(a)));
            
//            2ND WAY

//            thresh += double((1.262 * (double)img.at<Vec3b>(Point(i,j))[1])
//                    - (0.884*(double)img.at<Vec3b>(Point(i,j))[2])
//                    - (0.311 * (double)img.at<Vec3b>(Point(i,j))[0]));
        }
    }

    cout << thresh << endl;
    return 0;
}