Building Computer Vision Projects with OpenCV 4 and C++

Drawing the GUI elements

To display the current mode on the screen, let's create a function to draw text easily. OpenCV comes with a cv::putText() function with several fonts and anti-aliasing, but it can be tricky to place the text in the location that you want. Luckily, there is also a cv::getTextSize() function to calculate the bounding box around the text, so we can create a wrapper function to make it easier to place text.

We want to be able to place text along any edge of the window, make sure it is completely visible, and also to allow placing multiple lines or words of text next to each other without overwriting. So here is a wrapper function to allow you to specify either left-justified or right-justified, as well as to specify top-justified ...