Color Conversion

Code

import cv2

img = cv2.imread("input.jpg")

# BGR <-> RGB (for matplotlib)
rgb = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)

# BGR -> grayscale
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

# BGR -> HSV (good for color segmentation)
hsv = cv2.cvtColor(img, cv2.COLOR_BGR2HSV)

# Threshold a color range in HSV
lower = (35, 50, 50)
upper = (85, 255, 255)
mask = cv2.inRange(hsv, lower, upper)
green_only = cv2.bitwise_and(img, img, mask=mask)

# Lab for perceptual comparisons
lab = cv2.cvtColor(img, cv2.COLOR_BGR2LAB)
cv2.imwrite("mask.jpg", mask)

Explanation

OpenCV loads images in BGR order, so cvtColor with COLOR_BGR2RGB is needed before passing to libraries like matplotlib. HSV separates hue from intensity, making color-range masks robust to lighting changes. inRange produces a binary mask that bitwise_and uses to isolate a color.

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