Python Workshop: OpenCV
Based on:
http://www.dmi.unict.it/~furnari/teaching/CV1617/lab0/
Introduction
OpenCV (Open Source Computer Vision Library) is an open source computer vision and machine learning software library. OpenCV was built to provide a common infrastructure for computer vision applications and to accelerate the use of machine perception in the commercial products. [https://opencv.org/about/]
Basic usage
In [1]:
import matplotlib.pyplot as plt
import cv2 # opencv for python package
figsize = (10, 10)
In [2]:
# to run in google colab
import sys
if 'google.colab' in sys.modules:
import subprocess
subprocess.call('apt-get install subversion'.split())
subprocess.call('svn export https://github.com/YoniChechik/AI_is_Math/trunk/c_01_intro_to_CV_and_Python/Lenna.png'.split())
subprocess.call('svn export https://github.com/YoniChechik/AI_is_Math/trunk/c_01_intro_to_CV_and_Python/opencv_logo.png'.split())
This is how to read and plot an image with opencv
In [3]:
img = cv2.imread("Lenna.png")
In [4]:
plt.figure(figsize=figsize)
plt.imshow(img)
plt.title("Lenna orig")
Out[4]:
We got a weird image colors... This is because OpenCV uses image reading convention of BGR and matplotlib uses RGB.
The fix is easy:
In [5]:
img=cv2.cvtColor(img,cv2.COLOR_BGR2RGB)
plt.figure(figsize=figsize)
plt.imshow(img)
plt.title("Lenna RGB")
Out[5]: