Why Index out of range?

Hello everyone, I need assistance. I got an error "index exceeds matrix dimension"

with accessing the intensity of R, G and B components of an image. My code is as shown below:

rgb=imread('car3.jpg');  %# Load an RGB image
rgb=num2cell(rgb);
rPlane = zeros(size(rgb,1),size(rgb,2));
gPlane = zeros(size(rgb,1),size(rgb,2));
bPlane = zeros(size(rgb,1),size(rgb,2));

rPlane=[size(rgb,1),size(rgb,2)];
gPlane=[size(rgb,1),size(rgb,2)];
bPlane=[size(rgb,1),size(rgb,2)];

for i = 1:size(rgb,1) %rows
  for k=1:size(rgb,2) %columns
           rPlane=rgb{i,k}(:,:,1);% j=1(:,:,k);
           gPlane=rgb{i,k}(:,:,2);
           bPlane=rgb{i,k}(:,:,3);%j=3      
   end
end

The error occurs at "gPlane=rgb{i,k}(:,:,2);" inside the nested for loop. The car3.jpg picture has the following dimension: rgb(302,435,:)

Answer 1

[Walter Roberson]

The result of num2cell() is going to be a cell array which each entry is a single scalar value. You are trying to access the third dimension of that scalar.

[VicPeters]

Thank you Walter for the speedy response. But I am new to Matlab and will want you to explain further how I can extend the single entry to accommodate extra cells. Thanks once again.

[Walter Roberson]

rgb=imread('car3.jpg');  %# Load an RGB image
rPlane = rgb(:,:,1);
gPlane = rgb(:,:,2);
bPlane = rgb(:,:,3);

No loop needed.

[VicPeters]

Wao... it's so short? Thanks Walter, I remain very grateful to you!