python: want to display red channel only in opencv

27
votes

I am beginner in image processing. I am showing image in many color space the below code show the image in the 3 channels R G B however the image displayed in the gray layout. i need to display three images one with red channel as red image, another as blue, and the last one as green. thanks in advance.

# cspace.py
import cv2
import numpy as np

image = cv2.imread('download.jpg')

# Convert BGR to HSV
hsv = cv2.cvtColor(image, cv2.COLOR_BGR2HSV)
hsl = cv2.cvtColor(image, cv2.COLOR_BGR2HLS) # equal to HSL
luv = cv2.cvtColor(image, cv2.COLOR_BGR2LUV)


#RGB - Blue
cv2.imshow('B-RGB.jpg',image[:, :, 0])
cv2.imwrite('B-RGB.jpg',image[:, :, 0])

# RGB - Green
cv2.imshow('G-RGB',image[:, :, 1])
cv2.imwrite('G-RGB.jpg',image[:, :, 1])

# RGB Red
cv2.imshow('R-RGB',image[:, :, 2])
cv2.imwrite('R-RGB.jpg',image[:, :, 2])


cv2.waitKey(0)

Blue image as displayed currently

i need to display blue channel like this image

2
pythonopencvimage-processingcomputer-vision

2 Answers

42
votes

You can just make a copy of the original image and set some channels to 0.

import cv2

image = cv2.imread('download.jpg')

b = image.copy()
# set green and red channels to 0
b[:, :, 1] = 0
b[:, :, 2] = 0


g = image.copy()
# set blue and red channels to 0
g[:, :, 0] = 0
g[:, :, 2] = 0

r = image.copy()
# set blue and green channels to 0
r[:, :, 0] = 0
r[:, :, 1] = 0


# RGB - Blue
cv2.imshow('B-RGB', b)

# RGB - Green
cv2.imshow('G-RGB', g)

# RGB - Red
cv2.imshow('R-RGB', r)

cv2.waitKey(0)
2
votes
import cv2
import numpy as np

channel_initials = list('BGR')

image = cv2.imread('download.jpg')

for channel_index in range(3):
    channel = np.zeros(shape=image.shape, dtype=np.uint8)
    channel[:,:,channel_index] = image[:,:,channel_index]
    cv2.imshow(f'{channel_initials[channel_index]}-RGB', channel)
cv2.waitKey(0)