從 unsigned char 數組創建 cv::Mat 時出現分段錯誤

Question

我不明白為什么以下最小代碼輸出分段錯誤和 cv::Mat 值未正確打印：

#include <opencv2/opencv.hpp>

int main()
{
    unsigned char out[1280*720*3/2] = {100};
    cv::Mat dummy_query = cv::Mat(1, 1280*720*3/2*sizeof(unsigned char), CV_8UC1, (void *)out);
    cv::Size s = dummy_query.size();
    std::cout << s << "\r\n";
    for(int i = 0; i < 1280*720*3/2; i++)
    {
        std::cout << i << "ss" << int(out[i]) << ":";
        std::cout << dummy_query.at<int>(0,i) << " ";
    }
}

Answer 1

您已經在cv::Mat中定義了 uchar 數據類型，但在這一行訪問為 int std::cout << dummy_query.at<int>(0,i) << " ";

所以你的程序可能會在循環結束時崩潰，例如

// create a 100x100 8-bit matrix
Mat M(100,100,CV_8U);
// this will be compiled fine. no any data conversion will be done.
Mat_<float>& M1 = (Mat_<float>&)M;
// the program is likely to crash at the statement below
M1(99,99) = 1.f;

檢查這個打開的簡歷參考