Problem with Red And Blue

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Opencv uses BGR format to store data in memory

When image is save using imwrite then channels are in good order relatively to file extension (jpg, png, ....)

Mat img=imread("fruits.jpg",IMREAD_COLOR);
cout<<img.at<vec3b>(0,0);
imwrite("Fruitsopencv.png",img);

results 13,62,130 check in your favourite image editor : Blue=13 Green = 62 Red=130

In previous code i don't use cvtcolor to change bgr to rgb : when you use opencv function everything is done internally.