Loop in a array

2012 11 26
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Hi,
I have a question. I have an image with three bands. How can I apply a loop for do an operation to all the pixels?
image1=imread('image_1.tif'); %I've load the image. Has a length of 4x4x3
band1a= image_1(:,:,1);
band2a= image_1( :,:,2);
band3b= image_1(:,:,3);
for i = 1:numel(band1b)
(...) this is the part of the operation
output= ?
Thanks a lot in advance,

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Which operation u have to perform on all the pixels?
Emmanuelle
Emmanuelle 2012-11-26
Thanks for your reply Sabarinathan. It's an interpolation...
for i = 1:numel(band1b)
for i = 1:numel(banda2b)
...
and then inter= interp1(l1,l2,t2,'spline'))
...on the same pixel on the three bands and then, an operation of multiply for other variable to obtain one result.
oper1= b1abc.*interplan;
output1= sum(oper1);
And the output1 is the result for the operation.
Jan
Jan 2012-11-26
Please post a running piece of code. In the original question, "band1b" is not defined and we cannot guess its value. In the comment "l1, l2, t2, interplan, b1abc" is not defined.
Usually interpolations can be performed for a full vector or even a matrix directly without a loop.
Emmanuelle
Emmanuelle 2012-11-26
编辑：Emmanuelle 2012-11-27
I know it would be a bit confusing...
image1=imread('image_1.tif');
band1a= image1(:,:,1);
band2a= image1(:,:,2);
band3b= image1(:,:,3);
for i = 1:numel(band1b)
ma = zeros(100,1);
ma(10) = banda1b(i);
end
for i = 1:numel(band2b)
ma(25) = banda2b(i);
end
for i = 1:numel(band3b)
ma(50) = band3b(i);
end
vec1= [10, 25, 50]';
pos1= ma(10);
pos2= ma(25);
pos3= ma(50);
vec2= [pos1 pos2 pos3];
t= 0:100;
xi= 0:1:100;
interplan= interp1(vec1,vec2,t,'spline');
sp1_a= spb1y.*interplan; %I've defined sp1by before
sp1_b= sp1_a./spsum1;
sp2_a= spb2y.*interplan;
sp2_b= sp2_a./spsum2;
sp3_a= spb3y.*interplan;
sp3_b= spout3_a./spsum3;
spout1_c= sum(spout1_b);
spout2_c= sum(spout1_b);
spout3_c= sum(spout1_b);
I know it could be something confusing but what I want is to get this last three values (spout1_c, spout2_c and spout3_c) for every pixel, in every band.
Hope I've explain this well!
Emmanuelle
Emmanuelle 2012-11-27
The main problem is the following part because in an assignment A(I) = B, the number of elements in B must be the same but, I need to do it because it's important the 'position' in the interpolation.
for i = 1:numel(band1b)
ma = zeros(100,1);
ma(10) = banda1b(i);
end
for i = 1:numel(band2b)
ma(25) = banda2b(i);
end
for i = 1:numel(band3b)
ma(50) = band3b(i);
end

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回答（1 个）

Image Analyst
Image Analyst 2012-11-26

0 个投票

What is image_1? All you have shown up until that point is image1, which is a different variable.

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Emmanuelle
Emmanuelle 2012-11-27
Yes, you are right! It's the image.
image1=imread('image_1.tif');
band1a= image1(:,:,1);
band2a= image1(:,:,2);
band3b= image1(:,:,3);
Image Analyst
Image Analyst 2012-11-27
Regarding "I know it could be something confusing but what I want is to get this last three values (spout1_c, spout2_c and spout3_c) for every pixel, in every band." How about this:
image1(:, :, 1) = spout1_a;
image1(:, :, 2) = spout1_b;
image1(:, :, 3) = spout1_c;
Emmanuelle
Emmanuelle 2012-11-27
Thanks Image analyst! :) I've solved the problem starting the code like this:
for row= 1: nrows
for col= 1: ncols
for band= 1: nband
But now I don't know how it's possible to copy correctly the output. I've created my output matrix like this:
output= zeros(1200, 1202, 3);
And I want to copy the spout1_a to the first band (band1a), spout1_b to the second.... I'm trying with that but I get the following error: " Conversion to double from cell is not possible."
output(:,:,1)= {spout1_c}
Thanks!!

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Emmanuelle
Emmanuelle
2012-11-26

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