Book Image

OpenCV By Example

By : Prateek Joshi, David Millán Escrivá, Vinícius G. Mendonça
Book Image

OpenCV By Example

By: Prateek Joshi, David Millán Escrivá, Vinícius G. Mendonça

Overview of this book

Open CV is a cross-platform, free-for-use library that is primarily used for real-time Computer Vision and image processing. It is considered to be one of the best open source libraries that helps developers focus on constructing complete projects on image processing, motion detection, and image segmentation. Whether you are completely new to the concept of Computer Vision or have a basic understanding of it, this book will be your guide to understanding the basic OpenCV concepts and algorithms through amazing real-world examples and projects. Starting from the installation of OpenCV on your system and understanding the basics of image processing, we swiftly move on to creating optical flow video analysis or text recognition in complex scenes, and will take you through the commonly used Computer Vision techniques to build your own Open CV projects from scratch. By the end of this book, you will be familiar with the basics of Open CV such as matrix operations, filters, and histograms, as well as more advanced concepts such as segmentation, machine learning, complex video analysis, and text recognition.
Table of Contents (18 chapters)
OpenCV By Example
About the Authors
About the Reviewers

Adding slider and mouse events to our interfaces

Mouse events and slider controls are very useful in Computer Vision and OpenCV. Using these controls, users can interact directly with the interface and change the properties of their input images or variables.

In this section, we are going to introduce you to the concepts of adding slider and mouse events for basic interactions. To understand this correctly, we will create a small project, where we paint green circles in the image using the mouse events and blur the image with the slider:

// Create a variable to save the position value in track
int blurAmount=15;

// Trackbar call back function
static void onChange(int pos, void* userInput);

//Mouse callback
static void onMouse( int event, int x, int y, int, void* userInput );

int main( int argc, const char** argv )
  // Read images
  Mat lena= imread("../lena.jpg");
  // Create windows
  // create a trackbark
  createTrackbar("Lena", "Lena", &blurAmount...