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questions:
I am trying to use matplotlib read RGB image and convert it to grayscale.
In matlab, I use this:
img = rgb2gray(imread('image.png'));
In matplotlib tutorial they do not cover it. They just read in the image
import matplotlib.image as mpimg
img = mpimg.imread('image.png')
Then they sliced arrays, but this is not from what I understand of the RGB conversion to grayscale.
lum_img = img[:,:,0]
edit:
I find it hard to believe numpy or matplotlib no built-in function to convert from rgb to gray. This is not the common image processing operations in it?
I wrote a very simple function, it can use the imported image imread within 5 minutes. It is very inefficient, but that is why I hope that the built-Major.
Sebastian improved my capabilities, but I still hope to find a built-in.
matlab's (NTSC / PAL) to achieve:
import numpy as np
def rgb2gray(rgb):
r, g, b = rgb[:,:,0], rgb[:,:,1], rgb[:,:,2]
gray = 0.2989 * r + 0.5870 * g + 0.1140 * b
return gray
Reply:
How to use PIL
from PIL import Image
img = Image.open('image.png').convert('LA')
img.save('greyscale.png')
Matplotlib and use the formula
Y' = 0.299 R + 0.587 G + 0.114 B
You can do this:
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.image as mpimg
def rgb2gray(rgb):
return np.dot(rgb[...,:3], [0.299, 0.587, 0.114])
img = mpimg.imread('image.png')
gray = rgb2gray(img)
plt.imshow(gray, cmap = plt.get_cmap('gray'))
plt.show()
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