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Mastering OpenCV 4 with Python

You're reading from  Mastering OpenCV 4 with Python

Product type Book
Published in Mar 2019
Publisher Packt
ISBN-13 9781789344912
Pages 532 pages
Edition 1st Edition
Languages
Author (1):
Alberto Fernández Villán Alberto Fernández Villán
Profile icon Alberto Fernández Villán

Table of Contents (20) Chapters

Preface 1. Section 1: Introduction to OpenCV 4 and Python
2. Setting Up OpenCV 3. Image Basics in OpenCV 4. Handling Files and Images 5. Constructing Basic Shapes in OpenCV 6. Section 2: Image Processing in OpenCV
7. Image Processing Techniques 8. Constructing and Building Histograms 9. Thresholding Techniques 10. Contour Detection, Filtering, and Drawing 11. Augmented Reality 12. Section 3: Machine Learning and Deep Learning in OpenCV
13. Machine Learning with OpenCV 14. Face Detection, Tracking, and Recognition 15. Introduction to Deep Learning 16. Section 4: Mobile and Web Computer Vision
17. Mobile and Web Computer Vision with Python and OpenCV 18. Assessments 19. Other Books You May Enjoy

The coordinate system in OpenCV

To show you the coordinate system in OpenCV and how to access individual pixels, we are going to show you a low-resolution image of the OpenCV logo:

This logo has a dimension of 20 × 18 pixels, that is, this image has 360 pixels. So, we can add the pixel count in every axis, as shown in the following image:

Now, we are going to look at the indexing of the pixels in the form (x,y). Notice that pixels are zero-indexed, meaning that the upper left corner is at (0, 0), not (1, 1). Take a look at the following image, which indexes three individual pixels. As you can see, the upper left corner of the image is the coordinates of the origin. Moreover, y coordinates get larger as they go down:

The information for an individual pixel can be extracted from an image in the same way as an individual element of an array is referenced in Python. In the...

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