please tell me how to perform color transform

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Answer 1

[KL]

color_img = imread('image.png');
gray_img = rgb2gray(color_img);
imshow(gray_img)

Answer 2

[Image Analyst]

There are many color transform functions: rgb2gray(), ind2rgb(), rgb2lab(), rgb2hsv(), rgb2ycrcb(), makecform(), etc. And of course you could make up your own transform. Which do you want?

[Image Analyst]

I do not know what the axes represent. I do not know what colorization algorithm they are using. Sorry.