how to preserve RGB values of an image while making it gray image

I need to convert an RGB image to gray image, but after processing i want the image back to RGB,

So how can i preserve the RGB values of an image

I am using

RGBImage=imread('RGBImage.tiff')

to read the image

[Dyuman Joshi]

Store the image in a variable and use rgb2gray to store in another variable?

Answer 1

[DGM]

You don't. When you convert a color image to grayscale, you are discarding the color information. It's gone.

If you want to keep the color image, simply keep the color image and make a grayscale copy.

rgbpict = imread('peppers.png');
graypict = rgb2gray(rgbpict); % BT601 luma

If instead you intend to do some operations on the color image by using the grayscale image as a proxy, I'd have to know what kind of operation you're trying to do. If that's your intent, you'll have to describe the task.