Computer Vision Robotic Agents @ Allegheny College Janyl Jumadinova - - PowerPoint PPT Presentation

Computer Vision

Robotic Agents @ Allegheny College Janyl Jumadinova October 8, 2019

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Computer Vision

Make computers understand images and video.

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Computer Vision

Make computers understand images and video.

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Why computer vision matters?

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OpenCV

An open source BSD licensed computer vision library

• Patent-encumbered code isolated into “non-free” module (SIFT,

SURF, some of the Face Detectors, etc.) Available on all major platforms

• Android, iOS, Linux, Mac OS X, Windows

Written primarily in C++

• Bindings available for Python, Java, even MATLAB (in 3.0).

Documentation: http://docs.opencv.org Source: https://github.com/Itseez/opencv

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OpenCV

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OpenCV: Pixel

Grayscale: each pixel has a value between 0 (black) and 255 (white)

• values between 0 and 255 are varying shades of gray.

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OpenCV: Pixel

Grayscale: each pixel has a value between 0 (black) and 255 (white)

• values between 0 and 255 are varying shades of gray.

Color: pixels are normally represented in the RGB color space

• one value for the Red component, one for Green, and one for Blue,
• each of the three colors is represented by an integer in the range 0

to 255,

• how “much” of the color there is.

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OpenCV: Coordinate System

The point (0, 0) corresponds to the upper left corner of the image x value increases as we move to the right y value increases as we move down

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OpenCV: Image Representation

OpenCV represents images as NumPy arrays (matrices). NumPy is a library for the Python programming language that provides support for large, multi- dimensional arrays. To access a pixel value, we need to supply the x and y coordinates of the pixel. OpenCV actually stores RGB values in the order of Blue, Green, and Red.

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Images

How to input or output an image?

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Images

How to input or output an image?

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HighGUI: OpenCV Functions

namedWindow(winname, flags); Creates window accessed by its

• name. Window handles repaint and resize events.

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HighGUI: OpenCV Functions

namedWindow(winname, flags); Creates window accessed by its

• name. Window handles repaint and resize events.

destroyWindow(winname);: Destroys a window with the given name. destroyAllWindows();: Destroys all of the HighGUI windows.

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HighGUI: OpenCV Functions

namedWindow(winname, flags); Creates window accessed by its

• name. Window handles repaint and resize events.

destroyWindow(winname);: Destroys a window with the given name. destroyAllWindows();: Destroys all of the HighGUI windows. waitKey([delay]);: Waits for a key press; delay is in milliseconds.

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Video: OpenCV Functions

VideoCapture: Class for video capturing from video files, image sequences or cameras.

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Video: OpenCV Functions

VideoCapture: Class for video capturing from video files, image sequences or cameras. VideoWriter: Class for writing to video.

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• s

The os module in Python allows interaction with the Operating System, including environment variable manipulation and file system navigation.

• s.getcwd(): Get the current working directory.
• s.chdir(’/newdir’): Change cwd to newdir.
• s.listdir(path=.): List of everything in the present directory.
• s.path: contains functions for manipulating filenames and directory

names.

• s.path.join(): function constructs a path name out of one or

more partial path names. In this case, it simply concatenates strings. Calling this function will add an extra slash to the path name before joining it to the file name. This function can take any number of arguments.

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