OpenCV4

Overview

This is a tutorial on how to install OpenCV4 and use camera module.

Materials/Prerequisites

• Raspberry Pi

• Raspberry Pi Camera

Process

Install OpenCV

Follow these instruction to install OpenCV onto your Raspberry Pi using the terminal.

• Important note: don't do make-j4. It may freeze so it best to just do make or make-j1.

After you have successfully installed OpenCV, you will be able to use import cv2. If you do it on the terminal, you want to put in these code source ~/.profile and then workon cv.

Capturing image

Following these step to set up your camera

• Note: Ignoring GoPiGo installation.

Once the camera is set up, it is ready to take pictures. In order to capture image, follow these instruction

Taking picture code

Note:

• Use sleep (measured in seconds) to create a delay between the preview: time.sleep(seconds)

• Another way to enable your camera is: go to the terminal → type in sudo raspi-config → select Enable Camera → press Enter → select Finish → reboot and log back on to the Raspberry Pi.

Edge Detector

Once you have a picture, you may want to use edge detection to detect the chessboard region of interest.

Follow these instruction for Canny edge detection

• Note: Scroll down to the Explanation section.

In order to use build-in function in Open CV: remember to import cv2. In the instruction, the import cv2 ascv means that you can now type in cv instead of cv2 when using build-in function.

Use the following build-in code for Canny Detection:

Canny( detected_edges, detected_edges, lowThreshold, lowThreshold*ratio, kernel_size )

Ex: To load image:

• src = cv.imread(filename, cv.IMREAD_GRAYSCALE)

Then use:

• dst = cv.Canny(src, 50, 200, None, 3)

Houghline Transformation

Using the Canny Edge detection to find the region of interest(edges of the image) prior to the Houghline Transformation,one can now use the Hougline Tranformation: lines = cv.HoughLines(dst, 1, np.pi / 180, 150, None, 0, 0)

Authors

• Nhut Dang

• Robert Goodloe

• Ethan Shry(TA)

Fall 2018

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