How to loop on a data cube of an image

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Rawan hamdi
Rawan hamdi 2013-4-7
Hi, I'm trying to calculate gradient at each pixel in a data cube of an image an i'm getting this error "index out of bounds because size(X)=[280,307,191]."
Any help would be much appreciated Thank you
  2 个评论
Walter Roberson
Walter Roberson 2013-4-7
We are going to need to see some of your code.
Rawan hamdi
Rawan hamdi 2013-4-8
编辑：Walter Roberson 2013-4-8
Okay,here's my code below:
close all
Bands =191; %no of bands
pixels =280*307; %no of pixels
SIZE = [280,307 ,191]; %WxHxBands
lam = 0.063;
B=12;
X0 = multibandread('dc.tif', SIZE, 'int16',1252*2, 'bsq', 'ieee-le');
%adding noise
std_n=40; var_noise=std_n^2; % Gaussian noise standard deviation
reduced_pw = 1.5*var_noise; % power to reduce in first phase
std_n=sqrt(var(X0(:)));
Xn = randn(size(X0))*std_n; %noise
X = X0 + Xn; %Noisy Image
%looping on datacube
x = (X(1,:,1));
y = (X(:,1,1));
bands = X(1,1,:);
for i = 1:1: x
for j = 1:1: y
for k = 1 :1:bands
current_grad(i,j,k) = gradient(i,j,k);
end
end
end

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采纳的回答

Image Analyst
Image Analyst 2013-4-7
Somewhere in your code where you're indexing x, y, and z, the value(s) of at least one of those indexes is greater than 280, 307, and 191, respectively.

更多回答（2 个）

Walter Roberson
Walter Roberson 2013-4-8
You establish x, y, and bands according to the content of the noisy image, but then your triple nested for loop has you looping using those values as indices, such as in
for i = 1:1: x
Question: in your line
current_grad(i,j,k) = gradient(i,j,k);
is "gradient" the gradient function? If so then why are you applying the function to the indices i, j, k, rather than to the content of the image? And does it make sense to be applying the gradient function only to a point at a time?
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Walter Roberson
Walter Roberson 2013-4-8
Which MATLAB version are you using? And are you using the Student license?
Image Analyst
Image Analyst 2013-4-8
I cannot help you do the upgrade. You'll have to contact the Mathworks to do that.

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Rawan hamdi
Rawan hamdi 2013-4-8
编辑：Walter Roberson 2013-4-8
I've tried this:
x= squeeze(X(1,:,1));
y =squeeze(X(:,1,1));
b = X(1,1,:);
for i=1:x
for j =1 : y
for k = 1 :191
G = gradient(1:i,1:j,1:k);
end
end
end
but it keeps telling me 'Index exceeds matrix dimensions'
  2 个评论
Walter Roberson
Walter Roberson 2013-4-8
You establish x, and y according to the content of the noisy image, but then your triple nested for loop has you looping using those values as indices.
Also, you are overwriting G in each iteration of the triple-nested loop.
Rawan hamdi
Rawan hamdi 2013-4-8
Okay , could you help me fix the code?

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