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OpenCV Essentials

You're reading from   OpenCV Essentials Acquire, process, and analyze visual content to build full-fledged imaging applications using OpenCV

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Product type Paperback
Published in Aug 2014
Publisher
ISBN-13 9781783984244
Length 214 pages
Edition 1st Edition
Tools
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Toc

Table of Contents (10) Chapters Close

Preface 1. Getting Started FREE CHAPTER 2. Something We Look At – Graphical User Interfaces 3. First Things First – Image Processing 4. What's in the Image? Segmentation 5. Focusing on the Interesting 2D Features 6. Where's Wally? Object Detection 7. What Is He Doing? Motion 8. Advanced Topics Index

Selecting regions

Many computer vision applications require to focus interest inside local regions of the images. In that case, it is a very useful user tool to select the desired regions of interest (ROI). In the drawRs example, we show how to select, with the mouse, rectangular regions in the image to locally increase the contrast inside these regions (as shown in the following screenshot). For better control over region selection, we implement a click-and-drag behavior to reshape the rectangular boundary of each region.

Selecting regions

Output image with increased contrast in some rectangular regions

For the sake of simplicity, only the code corresponding to the function callback for mouse events is shown, since the rest is quite similar in the previous examples. The code is as follows:

void cbMouse(int event, int x, int y, int flags, void* userdata) {

  static Point p1, p2; // Static vars hold values between calls
  static bool p2set = false;

  if (event == EVENT_LBUTTONDOWN) { // Left mouse button pressed...
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