Book Image

Android Application Programming with OpenCV

By : Joseph Howse
Book Image

Android Application Programming with OpenCV

By: Joseph Howse

Overview of this book

Take a smartphone from your pocket, and within a few seconds, you can snap a photo, manipulate it, and share it with the world. You have just achieved mass production of image data. With a computer vision library such as OpenCV, you can analyze and transform copious amounts of image data in real time on a mobile device. The upshot to this is that you, as developers, can provide mobile users with many new kinds of images, constantly highlighting certain visual features that are of artistic or practical interest. Android is a convenient platform for such experiments because it uses a high-level language (Java), it provides standardized interfaces for sharing image data between applications, and it is mostly open source, so everyone can study its implementation. Android Application Programming with OpenCV is a practical, hands-on guide that covers the fundamental tasks of computer vision—capturing, filtering, and analyzing images-with step-by-step instructions for writing both an application and reusable library classes. Android Application Programming with OpenCV looks at OpenCV's Java bindings for Android and dispels mysteries such as which version of these bindings to use, how to integrate with standard Android functionality for layout, event handling, and data sharing, and how to integrate with OpenGL for rendering. By following the clear, concise, and modular examples provided in this book, you will develop an application that previews, captures, and shares photos with special effects based on color manipulation, edge detection, image tracking, and 3D rendering.Beneath the application layer, you will develop a small but extensible library that you can reuse in your future projects. This library will include filters for selectively modifying an image based on edge detection, 2D and 3D image trackers, and adapters to convert the Android system's camera specifications into OpenCV and OpenGL projection matrices. If you want a quick start in computer vision for Android, then this is the book for you. By the end of Android Application Programming with OpenCV, you will have developed a computer vision application that integrates OpenCV, Android SDK, and OpenGL.
Table of Contents (12 chapters)
Android Application Programming with OpenCV
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Mixing color channels


As we saw in Chapter 2, Working with Camera Frames, OpenCV stores image data in a matrix of type Mat, which is like a two-dimensional array. The columns and rows (specified by the first and second indices, respectively) correspond to the y and x pixel coordinates in the image. The elements are the pixel values. A pixel value may be represented by one number (in the case of a grayscale image) or multiple numbers (in the case of a color image). Each of these numbers is said to belong to a channel. A grayscale image may have just one channel, value (brightness), which is abbreviated as V. A color image may have as many as four channels—for example, red, green, blue, and alpha (transparency), which constitute the RGBA format. Other useful formats for color images include RGB (red, green, blue), HSV (hue, saturation, value), and L*a*b (luminosity, green-versus-magenta, yellow-versus-blue). In this book, we focus on RGB and RGBA images, but OpenCV supports other formats...