error: assignment dimension mismatch

I=imread('data (15).tif'); % Read an image

IG = rgb2gray(I);

[M,N] = size(IG);

G(:,:,2) = I(:,:,2);

G(:,:,1) = 0;

G(:,:,3) = 0;

Y = rgb2gray(G);

i have a image data base and when i run this code on my images,it work well on all of them except 2 of them which are horizontal images and biger then others,can any one help me plz? this is the error :

Subscripted assignment dimension mismatch.

Error in main (line 13) G(:,:,2) = I(:,:,2);

Answer 1

[Azzi Abdelmalek]

Try

clear G
G(:,:,2) = I(:,:,2);
G(:,:,1) = 0;
G(:,:,3) = 0;

[mohamad mohamad]

thank u so much for your instant answer

i wish the best for you