Python ModulesopencvIntroduction to OpenCV

Introduction to OpenCV

Learn everything there is to know about computer vision using Python and OpenCV.

OpenCV stands for Open Source Computer Vision. It was developed by Intel and later supported by Willow Garage. It is written in C++ but has Python, Java, and other bindings.

🧠 What is OpenCV?

OpenCV is a powerful toolkit used in:

  • Face detection and recognition
  • Object identification
  • Image filtering and enhancement
  • Real-time video analysis
  • Gesture recognition

📦 Installing OpenCV

MethodCommand
Basic installpip install opencv-python
Full install (includes extra modules)pip install opencv-contrib-python

🔍 Check Installation

import cv2
print("OpenCV version:", cv2.__version__)

📷 Reading, Displaying, and Saving Images

import cv2
print("Reading image...")
img = cv2.imread('example.jpg')
if img is None:
    print("Failed to load image.")
else:
    print("Image loaded successfully. Shape:", img.shape)
    cv2.imshow('Image', img)
    print("Displaying image. Waiting for key press...")
    cv2.waitKey(0)
    print("Key pressed. Closing all windows.")
    cv2.destroyAllWindows()
  • cv2.imread() reads the image
  • cv2.imshow() displays it
  • cv2.waitKey(0) waits for a key press
  • cv2.destroyAllWindows() closes all windows
⚠️

If the image window closes immediately, ensure that cv2.waitKey(0) is called before cv2.destroyAllWindows().

📝 Practice Questions

❓ Question 1

Display an image, wait for a key press, and then close the window.

Show Code
import cv2
print("Loading image...")
img = cv2.imread('sample.jpg')
if img is None:
    print("Failed to load image.")
else:
    print("Image shape:", img.shape)
    cv2.imshow('Output', img)
    print("Press any key to close window...")
    cv2.waitKey(0)
    print("Window closed.")
    cv2.destroyAllWindows()

❓ Question 2

Print the dimensions (shape) of an image.

Show Code
import cv2
print("Reading image for shape...")
img = cv2.imread('sample.jpg')
if img is None:
    print("Failed to load image.")
else:
    print("Shape of image:", img.shape)

❓ Question 3

Convert an image to grayscale and save it.

Show Code
import cv2
print("Reading image for grayscale conversion...")
img = cv2.imread('sample.jpg')
if img is None:
    print("Failed to load image.")
else:
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    print("Image converted to grayscale. Saving as 'gray.jpg'...")
    success = cv2.imwrite('gray.jpg', gray)
    if success:
        print("Grayscale image saved successfully.")
    else:
        print("Failed to save grayscale image.")

✅ Summary

  • Installed OpenCV using pip
  • Read and displayed images
  • Saved processed images
  • Printed shape and converted to grayscale
Requests Best Practices and TipsImage Arithmetic & Bitwise Operations