在opencv中獲取像素值與

Question

我已成功讀取帶有imread函數的灰度圖像，並試圖訪問al像素值並將它們複製到2D矢量。我收到此錯誤：

gray image channels: 1 
OpenCV Error: Assertion failed (dims <= 2 && data && (unsigned)i0 < (unsigned)si 
ze.p[0] && (unsigned)(i1 * DataType<_Tp>::channels) < (unsigned)(size.p[1] * cha 
nnels()) && ((((sizeof(size_t)<<28)|0x8442211) >> ((DataType<_Tp>::depth) & ((1 
<< 3) - 1))*4) & 15) == elemSize1()) in cv::Mat::at, file C:\opencv_3\opencv\bui 
ld\include\opencv2/core/mat.inl.hpp, line 894 

我不似乎明白了什麼是錯用下面的代碼：

Mat img = imread("C:\\digitalImageProcessing\\lion2.png", 0); 

if (!img.data)       
{ 
    cout << "Could not open or find the image" << std::endl; 
    return -1; 
} 


namedWindow("Gray image", CV_WINDOW_AUTOSIZE); 

// know the number of channels the image has 
cout << "gray image channels: " << img.channels() << endl; 

// ******************* READ the Pixel intensity ********************* 

int no_of_cols = img.cols; 
int no_of_rows = img.rows; 
int initial_value = 0; 

std::vector<std::vector<int>> image_matrix; 
image_matrix.resize(no_of_rows, std::vector<int>(no_of_cols,initial_value)); 

for (int j = 0; j < img.rows; j++) 
{ 
    for (int i = 0; i < img.cols; i++) 
    { 
     Scalar value = img.at<uchar>(i, j); 
     cout << "value = " << endl << " " << value.val[0] << endl << endl; 
     image_matrix[i][j] = intensity.val[0]; 
    } 
} 

Answer 1

可能是有一些比我下面的代碼更好的方式，但我認爲這可能是比你的每個像素的循環更好

#include "opencv2/opencv.hpp" 
#include "iostream" 

using namespace cv; 
using namespace std; 

int main() 
{ 
    Mat img = Mat(3,3,CV_8UC1); 
    randu(img,0,255); 

    cout << "img pixels \n\n" << img << endl; 

    vector<vector<int> > image_matrix; 
    vector<int> image_matrix_row; 

    for(int i = 0; i < img.rows; i++) 
    { 
     img.row(i).copyTo(image_matrix_row); 
     image_matrix.push_back(image_matrix_row); 
    } 
    cout << "\nimage_matrix[1][1] : " << image_matrix[1][1]; 
    return 0; 
} 

輸出：

img pixels 

[ 91, 2, 79; 
179, 52, 205; 
236, 8, 181] 

image_matrix[1][1] : 52