Learning OpenCV

Chapter 4. HighGUI

A Portable Graphics Toolkit

The OpenCV functions that allow us to interact with the operating system, the file system, and hardware such as cameras are collected into a library called HighGUI (which stands for "high-level graphical user interface"). HighGUI allows us to open windows, to display images, to read and write graphics-related files (both images and video), and to handle simple mouse, pointer, and keyboard events. We can also use it to create other useful doodads like sliders and then add them to our windows. If you are a GUI guru in your window environment of choice, then you might find that much of what HighGUI offers is redundant. Yet even so you might find that the benefit of cross-platform portability is itself a tempting morsel.

From our initial perspective, the HighGUI library in OpenCV can be divided into three parts: the hardware part, the file system part, and the GUI part. ^[38] We will take a moment to overview what is in each part before we really dive in.

The hardware part is primarily concerned with the operation of cameras. In most operating systems, interaction with a camera is a tedious and painful task. HighGUI allows an easy way to query a camera and retrieve the latest image from the camera. It hides all of the nasty stuff, and that keeps us happy.

The file system part is concerned primarily with loading and saving images. One nice feature of the library is that it allows us to read video using the same methods we would use to read a ...