Cannot get encoded image from cv :: imencode (getting mess). How to fix broken savings .jpg?

Question

So, I am trying to save an image in ostream via cv::imencode apis . From imencode we get a vector. As shown here , it can be saved in any stream. For example std::ofstream . But it does not flush data = (

This is what we see:

Here is what we get in the file:

And here is our code:

 #include <iostream> #include <fstream> #include <vector> #include <map> #include <string> #include <ctime> #include <iterator> #include <opencv2/opencv.hpp> void send_data(std::ostream & o, const std::vector<uchar> & v) { o.write(reinterpret_cast<const char*>(v.data()), v.size()); } int main( ) { int w=400, h=400; cv::Mat black = cv::Mat::zeros(cv::Size(w, h), CV_8UC3); { for(int i = 0; i <= 35; ++i) { for (int k = 0; k <=35; ++k) { black.row(i).col(k) = 255; } } for(int i = 10; i <= 15; ++i) { for (int k = 10; k <=15; ++k) { black.row(i).col(k) = 0; } } for(int i = 25; i <= 30; ++i) { for (int k = 25; k <=30; ++k) { black.row(i).col(k) = 0; } } for(int i = 25; i <= 75; ++i) { for (int k = 25; k <= 75; ++k) { black.row(i).col(k) = 255; } } for(int i = 35; i <= 65; ++i) { for (int k = 35; k <=65; ++k) { black.row(i).col(k) = 0; } } for(int i = 57; i <= 62; ++i) { for (int k = 57; k <=62; ++k) { black.row(i).col(k) = 255; } } for(int i = 90; i <= 99; ++i) { for (int k = 90; k <=99; ++k) { black.row(i).col(k) = 255; } } } cv::namedWindow( "Components", CV_WINDOW_AUTOSIZE ); cv::imshow( "Components", black ); std::vector<uchar> buff; std::vector<int> p; p.push_back(CV_IMWRITE_JPEG_QUALITY); p.push_back(9); cv::imencode(".jpg", black, buff); std::ofstream outfile ("test.jpg"); send_data(outfile, buff); outfile.close(); cv::waitKey(0); std::cin.get(); return 0; } 

Answer 1

You need to open the output file in binary mode.

 std::ofstream outfile ("test.jpg", std::ofstream::binary);