cant add matrices of same dimensions

im trying to add an image to a matrix of ones for which i have used the following code:

c=imread('C:\Users\Richik\Desktop\ima.png');
[x,y]=size(c)
m=ones(x,y);
g=m+c;

but even when the matrix dimensions are same,im getting this error:

??? Error using ==> plus
Matrix dimensions must agree.

i cant figure out why this is happening.....

Answer 1

[Walter Roberson]

Chances are that your PNG image is an RGB image and so is 3 dimensional. You should look at

s = size(c)
[x,y] = size(c)

and I think you will find that y is not equal to s(2). Read the documentation for size() to understand why not.

[Terry McGinnis]

[x,y]=size(c)
m=ones(x,y);
[u,v]=size(m)

i get this:

x =

     512

y =

          1536

u =

     512

v =

          1536

and after using rgb2gray() and then calculating the size i get:

x =

     512

y =

     512

u =

     512

v =

     512

yet when i'm doing this operation:

e=c+m;
subplot(3,3,3);
imshow(e);
title('addition');

i'm getting a fully white image. shouldnt the output be a little brighter version of the original image?

[Walter Roberson]

http://www.mathworks.com/help/matlab/ref/size.html

[d1,d2,d3,...,dn] = size(X), for n > 1, returns the sizes of the dimensions of the array X in the variables d1,d2,d3,...,dn, provided the number of output arguments n equals ndims(X). If n does not equal ndims(X), the following exceptions hold:

n < ndims(X) di equals the size of the ith dimension of X for 0<i<n, but dn equals the product of the sizes of the remaining dimensions of X, that is, dimensions n through ndims(X).

[Walter Roberson]

A change of 1/256 in the brightness of an image is not necessarily going to be very noticeable, especially if you have not used a full 256 entry colormap

colormap(gray(256))

[Terry McGinnis]

thank u

Answer 2

[Eng. Fredius Magige]

Hi It has to follow its rule, and might be g=[m,c];

[Walter Roberson]

That would, if it worked, append c after m, not add 1 to each element of c.