Convert image numpy array into grayscale array directly without saving image

Question

I have a NumPy array img_array of dimension (h,w,3) of one image, which is the result of some function. I want to convert this NumPy array directly into grayscale.

Possible Solution: Save the img_array as image using cv2.imwrite(path). Then read again with cv2.imread(path, cv2.GRAYSCALE)

However, I am looking for something like this :

def convert_array_to_grayscale_array(img_array):
        do something...
        return grayscare_version

I have already tried cv2.imread(img_array, CV2.GRAYSCALE), but it is throwing error of img_array must be a file pathname.

I think saving a separate image will consume more space disk. Is there any better way to do that with or without using the OpenCV library function.

Does this answer your question? Converting Numpy Array to OpenCV Array — Yunus Temurlenk
– Yunus Temurlenk, Commented Aug 11, 2020 at 10:42
You can do it directly in Numpy - see last line here stackoverflow.com/a/58531115/2836621 — Mark Setchell
– Mark Setchell, Commented Aug 11, 2020 at 10:44

perlusha · Accepted Answer · 2020-08-11 10:42:36Z

1

scikit-image has color conversion functions: https://scikit-image.org/docs/dev/auto_examples/color_exposure/plot_rgb_to_gray.html

from skimage.color import rgb2gray

grayscale = rgb2gray(img_array)

answered Aug 11, 2020 at 10:42

perlusha

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