python operates the camera based on opencv

To use the camera, you need to create a VideoCapture object using (0), the parameter 0 refers to the number of the camera, if you have two cameras on your computer, you can pass in 1 for accessing the 2nd camera, and so on.

# Turn on the camera and gray out the display
import cv2 as cv 
# 0 indicates the camera number
capture = (0)

while(True):
  # Get a frame
  # The first parameter ret (abbreviation for return value) is a boolean value indicating whether the current frame was acquired correctly or not.
  ret, frame = ()
  # Convert this frame to grayscale
  gray = (frame, cv.COLOR_BGR2GRAY)

  ('frame', gray)
  if (1) == ord('q'):
    break

The camera captures the image:

Getting and modifying camera property values

With (propId) you can get some properties of the camera, such as captured resolution, brightness and contrast, etc. propId is a number from 0 to 18, representing different properties. To modify the value of the camera's properties, you can use (propId,value). For example, if we add the following code before while, we can capture the video with 2x resolution relative to the above.

# Get the resolution of the capture
# propId can be written directly as a number, or in OpenCV notation
width, height = (3), (4)
print(width, height)

# Captured at double the original resolution
(cv.CAP_PROP_FRAME_WIDTH, width * 2)
(cv.CAP_PROP_FRAME_HEIGHT, height * 2)

Captured at 2x the resolution of the original image:

Play local video

Same as turning on the camera, if you replace the camera number with the path to the video you can play the local video. Recall that (), its parameter indicates the pause time, so the larger this value is, the slower the video will play, and vice versa, the faster it will play, usually set to 25 or 30.

# opencv playback of local video
import cv2 as cv

capture = ('E:/1.mp4')

while(()):
  ret, frame = ()
  gray = (frame, cv.COLOR_BGR2GRAY)

  ('frame', gray)
  if (30) == ord('q'):
    break

E:/1.mp4 in playback:

Record video and save it

Previously we used () to save images, to save videos we need to create a VideoWriter object and we need to pass it four parameters:
1. The name of the output file, such as ''
2. Coding mode FourCC code
3. Frame rate FPS
4. Resolution size to be saved
FourCC is a four-byte code used to specify how the video is encoded. For example, MJPG encoding can be written like this: cv.VideoWriter_fourcc(*'MJPG') or cv.VideoWriter_fourcc('M','J','P','G')

import cv2 as cv

capture = (0)

# Define the encoding method and create the VideoWriter object
fourcc = cv.VideoWriter_fourcc(*'MJPG')
outfile = ('', fourcc, 25., (640, 480))

while(()):
  ret, frame = ()

  if ret:
    (frame) # Write the file
    ('frame', frame)
    if (1) == ord('q'):
      break
  else:
    break

As expected it was generated under the current path :

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