shifting an image vertically down.

Hi, I want to shift a picture vertically down by 50 pixels here is my code:

X=imread('photo1.jpg');
X_double=double(X);
[m,n]=size(X_double);
E=eye(n);
T=zeros(n,n);
r=50;
T(1:r,:)=E(n-(r-1):n,:);
T(r+1:n,:)=E(1:n-r,:);
X_shift=T*X_double

I'm trying to make a transformation matrix and then multiply the resulting matrix by the image matrix "X". I keep getting an error though:

"Error using , inputs must be 2-D, or at least one input must be scalar. To compute elementwise TIMES, use TIMES (.) instead."

Any help is much appreciated, thanks.

[Adam]

What are you wanting to happen to the bottom 50 pixels and what is supposed to fill the 50 left at the top? I don't see why you are trying to do a multiplicative transform just to shift an image.

Can't you just concatenate the image vertically with 50 rows of zeros?

Answer 1

[Walter Roberson]

You need to do the three color planes separately, because matrix multiplication is not defined for 3D arrays (RGB images are 3D arrays)

Answer 2

[Image Analyst]

Why not use imtranslate()???