Recovery of RGB from a Converted RGB2Gray converted image

Hello, I have browsed the previous attempt for recovering RGB truecolor from grayscale image but have not found a solution that is satisfying so I will post this.

I have an application where I need to process a number of images at different exposures to obtain a sensor response function. To do this, I must make sure that the images are orthorectified. To do this I had to convert them to Grayscale to obtain the affine transformations. I have successfully done this. Now I want to apply the color back into the grayscales from the original images. I thought I would start simple, first with a simple grayscale to RGB recovery. It seems that the best way to do this is to convert the rgb images to indexed images. This is my attempt. Its kinda weird while I have only specified a red channel, I am getting blue and green coming in the resulting recovered RGB image. Any thoughts?

A=imread('DSC08069.JPG');

AmapR=A(:,:,1);

AmapG=A(:,:,2);

AmapB=A(:,:,3);

B=rgb2gray(A);

imshow(B);

Bind=gray2ind(B);

RGB_Aback=ind2rgb(Bind,AmapR);

imshow(RGB_Aback);

[thiirane]

O.K. I believe I can achieve the rectification using and indexed image. Thank for the feedback.

Yes... I see that I used the rgb2ind incorrectly... I have been working with it after this post. I also concur that I will not be able to colorize the registered index image. That's too bad. Thank you.

[Image Analyst]

I believe you can't. At best you'll get a posterized image (with only 64 colors since you didn't specify a number in gray2ind). You didn't even use ind2rgb correctly. The second argument is supposed to be a colormap, not an image.

[Image Analyst]

You can colorize it, but not with the original colors. But you shouldn't say "that's too bad" because you don't need to colorize your registered image. Like I said, you still have your original color image. You can register that if you want - you are not stuck with just registering only your gray scale image.

[thiirane]

I figured out how to rectify the image by simply performing the affine2d adjustments on the individual channels then reassembling them. Sorry for being slow. I appreciate your help.

Answer 1

[Image Analyst]

You still have the RGB image - it's in the badly-named "A". So there is no need to recover it from the grayscale version of it. You can't even do that - that's why you couldn't find any method via your searching.