How do I write a
cv::imwrite() function correctly writes an image file if the input
cv::Matis in BGR order (which is the case if you let OpenCV create it). If you created the image by yourself, you have to convert the color ordering before, for example by calling as suggested by bamboove
cv::cvtColor(in, out, CV_RGB2BGR); if you created an RGB image.
(Pay attention to the color conversion code, it's slightly different from bamboon's.)