Now that we know how to capture a live video stream from the webcam, let's see how to use the keyboard to interact with the window displaying the video stream.
import argparse
import cv2
def argument_parser():
parser = argparse.ArgumentParser(description="Change color space of the
input video stream using keyboard controls. The control keys are:
Grayscale - 'g', YUV - 'y', HSV - 'h'")
return parser
if __name__=='__main__':
args = argument_parser().parse_args()
cap = cv2.VideoCapture(0)
# Check if the webcam is opened correctly
if not cap.isOpened():
raise IOError("Cannot open webcam")
cur_char = -1
prev_char = -1
while True:
# Read the current frame from webcam
ret, frame = cap.read()
# Resize the captured image
frame = cv2.resize(frame, None, fx=0.5, fy=0.5, interpolation=cv2.INTER_AREA)
c = cv2.waitKey(1)
if c == 27:
break
if c > -1 and c != prev_char:
cur_char = c
prev_char = c
if cur_char == ord('g'):
output = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
elif cur_char == ord('y'):
output = cv2.cvtColor(frame, cv2.COLOR_BGR2YUV)
elif cur_char == ord('h'):
output = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
else:
output = frame
cv2.imshow('Webcam', output)
cap.release()
cv2.destroyAllWindows()This program will display the input video stream and wait for the keyboard input to change the color space. If you run the previous program, you will see the window displaying the input video stream from the webcam. If you press G, you will see that the color space of the input stream gets converted to grayscale. If you press Y, the input stream will be converted to YUV color space. Similarly, if you press H, you will see the image being converted to HSV color space.
As we know, we use the function
waitKey() to listen to the keyboard events. As and when we encounter different keystrokes, we take appropriate actions. The reason we are using the function ord() is because waitKey() returns the ASCII value of the keyboard input; thus, we need to convert the characters into their ASCII form before checking their values.