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](https://stackoverflow.com/questions/7587490/converting-numpy-array-to-opencv-array) — Yunus Temurlenk, Aug 11 '20 at 10:42
You can do it directly in Numpy - see last line here https://stackoverflow.com/a/58531115/2836621 — Mark Setchell, Aug 11 '20 at 10:44

score 1 · Accepted Answer · answered Aug 11 '20 at 10:42

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 '20 at 10:42

perlusha

153
6

Convert image numpy array into grayscale array directly without saving image

1 Answers1