Mastering OpenCV 3 - Second Edition

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 correct 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 and make sure it is completely visible and also to allow placing multiple lines or words of text next to each other without overwriting each other. So here is a wrapper function to allow you to specify either left-justified or right-justified, as ...