opencv-python

haarcascade_frontalface_default.xml: Trained XML classifiers describes some features of some object we want to detect a cascade function is trained from a lot of positive(faces) and negative(non-faces) images.

Image

• Read an image from file (using cv::imread)
• Display an image in an OpenCV window (using cv::imshow)

• Write an image to a file (using cv::imwrite)

• IMREAD_COLOR loads the image in the BGR 8-bit format. This is the default that is used here.

• IMREAD_UNCHANGED loads the image as is (including the alpha channel if present)

• IMREAD_GRAYSCALE loads the image as an intensity one

• core section, as here are defined the basic building blocks of the library

• imgcodecs module, which provides functions for reading and writing
• highgui module, as this contains the functions to show an image in a window

Video

VideoCapture()

VideoWriter()

Drawing

• Learn to draw different geometric shapes with OpenCV
• You will learn these functions :
  • cv.line(), cv.circle() , cv.rectangle(), cv.ellipse(), cv.putText() etc.

img, color, thikness, linType

Mouse

Learn to handle mouse events in OpenCV You will learn these functions : cv.setMouseCallback()

['EVENT_FLAG_ALTKEY', 'EVENT_FLAG_CTRLKEY', 'EVENT_FLAG_LBUTTON', 'EVENT_FLAG_MBUTTON', 'EVENT_FLAG_RBUTTON', 'EVENT_FLAG_SHIFTKEY', 'EVENT_LBUTTONDBLCLK', 'EVENT_LBUTTONDOWN', 'EVENT_LBUTTONUP', 'EVENT_MBUTTONDBLCLK', 'EVENT_MBUTTONDOWN', 'EVENT_MBUTTONUP', 'EVENT_MOUSEHWHEEL', 'EVENT_MOUSEMOVE', 'EVENT_MOUSEWHEEL', 'EVENT_RBUTTONDBLCLK', 'EVENT_RBUTTONDOWN', 'EVENT_RBUTTONUP']

Trackbar

For cv.createTrackbar() function, first argument is the trackbar name, second one is the window name to which it is attached, third argument is the default value, fourth one is the maximum value and fifth one is the callback function which is executed every time trackbar value changes. The callback function always has a default argument which is the trackbar position. In our case, function does nothing, so we simply pass.

Another important application of trackbar is to use it as a button or switch. OpenCV, by default, doesn't have button functionality. So you can use trackbar to get such functionality. In our application, we have created one switch in which application works only if switch is ON, otherwise screen is always black.

Operations on Images

• Basic Operations on Images

  • Learn to read and edit pixel values, working with image ROI and other basic operations.

• Arithmetic Operations on Images

  • Perform arithmetic operations on images

• Performance Measurement and Improvement Techniques

  • Getting a solution is important. But getting it in the fastest way is more important. Learn to check the speed of your code, optimize the code etc.

Image Processing

Feature Detection and Description

Video Analysis