OpenCV:Basic

lastmod 2023-10-26created 2023-01-076 edits

OpenCV basics.

Curriculum

1. Python basics
2. NumPy basics
3. Reading and writing images with cv2.imread/cv2.imwrite
4. Displaying in a window with cv2.imshow
5. Learning OpenCV:Drawing skills such as cv2.rectangle
6. Reading video and displaying it in a window using cv2.VideoCapture
   • Getting keyboard events with cv2.waitKey/cv2.waitKeyEx
7. Saving video with cv2.VideoWriter
8. Image binarization with cv2.threshold
9. OOP
10. Turning the above into classes
11. Selecting an ROI region with cv2.selectROI
12. Drawing on an ROI region using NumPy slices
13. Implementing an ROI selector without cv2.selectROI
    • Select an ROI with the mouse using cv2.setMouseCallback, then draw only that region with cv2.threshold
    • Pass the threshold value of cv2.threshold dynamically from the keyboard
14. Contour extraction using cv2.findContours and drawing with cv2.drawContours

Typical image processing sequence

1. Conversion to the grayscale color space using cv2.cvtColor.
2. Image binarization with cv2.threshold
3. Noise removal using dilation/erosion morphological operations with cv2.erode, cv2.dilate, cv2.morphologyEx
4. Image Contours (image contour extraction)
   • Or edge extraction using cv2.Canny.
   • Contour extraction using cv2.findContours and drawing with cv2.drawContours
   • Line/circle detection using the Hough transform
   • Approximating contour shapes using cv2.approxPolyDP
   • Minimum-area rotated rectangle with cv2.minAreaRect
   • Convex hull - outermost contour detection

Final stage

• cvtoolkit

See also

• OpenCV

Favorite site

• OpenCV - basic operations - Cornor’s Blog