Computing pixels value(Uk,Uj) from U -Image in YUV color Space

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Algorithms Analyst
Algorithms Analyst 2013-2-20
评论： iup geii amiens 2014-5-20
Hi everyone
I want to compute the pixel values let say Uk and Uj from UImage.Here is my code in which I am doing indexing.
UImage=imread(Uimage);
B=ones(length(UImage));
slidingwindow=conv2(B,UIimage,'same');%this part computes only centre pixels.
[pixelrow pixelcol]=size(slidingwindow);%Pixelrow and pixelcol are center pixels of window
for windrow=-1:1
row=pixelsrow+windrow;
for windcol=-1:1
col=pixelscol+windcol;
%% here I need some piece of code further May be Uk=UImage(row,col)???????????
end end
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iup geii amiens
iup geii amiens 2014-5-20
Hello Sir,
I am working on the same sheet. Please can i have your code and we may help each other :D
I will be grateful Have a nice day

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回答（2 个）

Thorsten
Thorsten 2013-2-20
To get the pixel values of a gray scale image
I = imread('cameraman.tif');
x = 20; y = 30;
Ixy = I(y, x);
To get the G pixel value of an RGB image
I = imread('peppers.png');
IGxy = I(y, x, 2);
Same should work for your U image if you have stored just the U channel or all three channels in your image.
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Thorsten
Thorsten 2013-2-20
编辑：Thorsten 2013-2-20
I assume that you refer to the paper http://philippe.noriega.free.fr/fichiers/visapp06.pdf
Then x and y are the location in the image where you compute your histograms. n = 12 is the size of your subwindow that is applied with a gap of 3 to your image.
To slide your window, use
gap = 3;
for x = 1:gap:size(I, 1)
for y = 1:gap:size(I, 2)
ind1 = y-n/2:y+n/2;
ind2 = x-n/2:x+n/2;
And for each location you need a third loop over the number of bins in your histogram
for j = 1:Nbins
dU = Uk(:) - Uval(j);
dV = Vk(:) - Vval(j);
Gj = Kj*exp(-(Du.^2+Dv.^2)/(2*sigma^2));
CH(x, y, j) = Gj;
end
end
end

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Image Analyst
Image Analyst 2013-2-20
Your code is all wrong. Try this:
UImage=imread(Uimage);
windowSize = 5;
sigma = whatever.....
kernel = fspecial('gaussian', windowSize, sigma);
slidingwindow=conv2(UIimage, kernel ,'same');
You don't need double for loops after that - conv2 does the sliding window filtering so it's already done. No need to try to do it again manually.
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Image Analyst
Image Analyst 2013-2-20
Correct, but I haven't really tried to understand what the algorithm does. You're just blurring the U channel. Not sure if that's part of the algorithm or not - I'm just going by what you said.
Algorithms Analyst
Algorithms Analyst 2013-2-21
Yeah. That's so interesting.In the color Gaussian kernel part of the algorithm two other pixels values from i and j locations are computed and they are VJ and Vk respectively.So I think they are taking just UV image from YUV colorspace by ignoring Y channel and computing the color gaussain kernel in UV color space.But anyway thanks for your time and concern.
Thanksssss......cheers..

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