Hue cycling effect on webcam footage with Python

Question

I am trying to create a program in Python that retrieves webcam footage and applies a slow and constant change in hue, similar to a hue cycling effect. Additionally, I am wondering if it would be possible to apply the hue cycle only to the color green in the webcam footage, though I am unsure how to detect the color in the frame and apply the cycle only to that color.

I have tried playing around with this code I found, though it gets applied to the whole frame and on the output in certain spots discoloration/weird spots depending on the part of the cycle it is on.

import cv2
import numpy as np

# Initialize video capturer
cap = cv2.VideoCapture(0)

# Set frame width and height
frame_width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
frame_height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))

# Initialize angle for hue rotation
angle = 0

while True:
    # Capture frame
    ret, frame = cap.read()

    # Convert frame to HSV color space
    hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)

    # Split channels
    h, s, v = cv2.split(hsv)

    # Increment angle
    angle = (angle + 1) % 360

    # Rotate hue channel
    h = (h + angle) % 180

    # Merge channels back to HSV image
    hsv = cv2.merge((h, s, v))

    # Convert back to BGR color space
    result = cv2.cvtColor(hsv, cv2.COLOR_HSV2BGR)

    # Display frame
    cv2.imshow("Webcam", result)

    # Check for user input
    key = cv2.waitKey(1)
    if key == 27: # Esc key
        break

# Release video capturer
cap.release()

# Close all windows
cv2.destroyAllWindows()

Answer 1

You can detect the color green in the frame using color thresholds and a mask. To detect the color green try the inRange function:

import cv2
import numpy as np

# Initialize video capturer
cap = cv2.VideoCapture(0)

# Set frame width and height
frame_width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
frame_height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))

# Initialize angle for hue rotation
angle = 0

while True:
    # Capture frame
    ret, frame = cap.read()

    # Convert frame to HSV color space
    hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)

    # Split channels
    h, s, v = cv2.split(hsv)

    # Define lower and upper bounds for green color
    lower_green = np.array([50, 50, 50])
    upper_green = np.array([70, 255, 255])

    # Create mask for green color
    mask = cv2.inRange(hsv, lower_green, upper_green)

    # Increment angle
    angle = (angle + 1) % 360

    # Rotate hue channel only for green pixels
    h[mask != 0] = (h[mask != 0] + angle) % 180

    # Merge channels back to HSV image
    hsv = cv2.merge((h, s, v))

    # Convert back to BGR color space
    result = cv2.cvtColor(hsv, cv2.COLOR_HSV2BGR)

    # Display frame
    cv2.imshow("Webcam", result)

    # Check for user input
    key = cv2.waitKey(1)
    if key == 27: # Esc key
        break

# Release video capturer
cap.release()

# Close all windows
cv2.destroyAllWindows()