How to convert QImage to opencv Mat

Question

I have searched on the internet but I cannot find a method of converting a QImage(or QPixmap) to a OpenCV Mat. How would I do this?.

Answer 1

One year after you issued this question there've been great answers on the internet:

• Convert between cv::mat and Qimage correctly
• Converting Between cv::Mat and QImage or QPixmap

But the way I see it, if you're working with Qt and OpenCV at the same time then type QImage is probably just for displaying, that case you might want to use QPixmap since it's optimized for displaying. So this is what I do:

1. Load image as cv::Mat, if you'd like to display the image, convert to QPixmap using the non-copy method introduced in the second article.
2. Do your image processing in cv::Mat.
3. Any time during the workflow you can call upon something like Mat2QPixmap() to get realtime result.
4. Never convert QPixmap to cv::Mat, there's no sense doing it considering the purpose of each type.