# Machine Vision

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## pca implemetation on an image

hi, i want to perform pca on an image to get luminance image. i have done the same thing in matlab and now want to implement it in labview. but i m so confused,,, i have used imaqcolorimagetoarray vi to convert image first to array and then apply pca on it... but the array of rgb image is a 2d matrix but in matlab it is a 3d matrix,, the result of pca here and princomp in matlab is also different ... plz tell me how can i get it,,   thnx ,, here is the  code for pca in matlab

it is a function that is called in the original program ....

function [luminance] = PCA1(RGB)

% USAGE [luminance channel] = PCA1(RGB)
%
% INPUT
% RGB: rgb image
% OUTPUT
% luminance channel:
%

% from matrix representation to vector

r = RGB(:,:,1);
g = RGB(:,:,2);
b = RGB(:,:,3);

[rS cS d] = size(RGB)

rVec = r(;
gVec = g(;
bVec = b(;
Ivec = cat(2,rVec,gVec,bVec);

% compute eigen vector
[eigenVec score eigenVal ts] = princomp(Ivec);
% the luminance is normalized to 1
V = eigenVec/(sum(eigenVec(:,1)));

% transformation from RGB to PCA representation
Bvec = Ivec*V

% from vector representation to matrix
luminance = reshape(Bvec(:,1),rS,cS)

plz help me as i m new in labview :-(

Message 1 of 8
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## Re: pca implemetation on an image

The easiest way to get the luminance plane is to call IMAQ ExtractColorPlanes or IMAQ ExtractSingleColorPlane.

Message 2 of 8
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## Re: pca implemetation on an image

yup i kow thai is easiest way, but problem is that i have to get luminance image by applying PCA

is there any method to apply PCA on an image directly

i have first change the image in array form but that is a 2d array but in matlab that is 3d array for an image how can i get a 3d array of an image direct.. where the 3rd dimension shows the RGB values

plz plz help me

Message 3 of 8
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## Re: pca implemetation on an image

why nobody replied me ??????//

plzzzzzzzzzzzzzzzz tell me

Message 4 of 8
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## Re: pca implemetation on an image

You can use a combination of IMAQ ExtractColorPlanes, IMAQ ImagetoArray, IMAQ ColorImagetoArray and NI_AALPro.lvlib:Eigenvalues and Vectors (located in the Mathematics>>Linear Algebra palette) to implement the algorithm you described.

Message 5 of 8
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## Re: pca implemetation on an image

thnx

but what is the ni-aalprovi?

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## Re: pca implemetation on an image

NI_AALPro.lvlib refers to the Advanced Analysis LabVIEW Library that the VI belongs to. You can find it in the Mathematics>>Linear Algebra palette.

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## Re: pca implemetation on an image

i have done my work but here is a problem. i want to get luminance image by applying pca but the resultant image is not clear. here is the attached vi. would u plz  usee it and correct it for me?