I have an image and I need to extract local features,so I divided it to 16 blocks and size of each block =64 *64 pixels and extract that three color histograms features locally from each block, now I need to

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teja jayavarapu 2018-1-24

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https://ww2.mathworks.cn/matlabcentral/answers/378666-i-have-an-image-and-i-need-to-extract-local-features-so-i-divided-it-to-16-blocks-and-size-of-each-b

评论： teja jayavarapu 2018-1-24

tic
disp('query')
[filename, pathname]=uigetfile({'*.jpg'},'queryimage');
img=strcat(pathname,filename);
a=imread(img);
subplot(4,5,3)
imshow(img)
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0.05 1 0.95]);
[r, c, numOfBands] = size(a);
%dividing image into 8x8 subblocks
bs=64;%block size
nob=(r/bs)*(c/bs);%Total no of blocks
k=0;
for i=1:(r/bs)
    for j=1:(c/bs)
        T=k+j;
        T=num2str(T);
        C=strcat(b,T);
        col1=bs*(j-1)+1;
        row1=bs*(i-1)+1;
        col2=bs*(j-1)+bs;
        row2=bs*(i-1)+bs;
       C=imcrop(a,[col1 row1 col2 row2]);   
    end
    k=k+(r/bs);
end
b = rgb2hsv(b);
% split image into h, s & v planes
h = b(:, :, 1);
s = b(:, :, 2);
v = b(:, :, 3);
% Create the histogram quantized into 8×3×3 bins
X= zeros(8, 3, 3);
for k = 1 : numel(h)
  indexH = floor(8 * h(k)) + 1;
  indexS = floor(3 * s(k)) + 1;
  indexV = floor(3 * v(k)) + 1;
  if indexH > 8
    indexH = 8;
  end
  if indexS > 3
    indexS = 3;
  end
  if indexV > 3
    indexV = 3;
    end
    X(indexH, indexS, indexV) = X(indexH, indexS, indexV) + 1;
end

#so, i want to quantify each block in the above manner i want to do for every block and store the 16 blocks matrices into resultant matrix G, how i do that

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Walter Roberson 2018-1-24

在 MATLAB Online 中打开

You have

for i=1:(r/bs)
    for j=1:(c/bs)
        T=k+j;
        T=num2str(T);
        C=strcat(b,T);
        col1=bs*(j-1)+1;
        row1=bs*(i-1)+1;
        col2=bs*(j-1)+bs;
        row2=bs*(i-1)+bs;
       C=imcrop(a,[col1 row1 col2 row2]);   
    end
    k=k+(r/bs);
end

Every iteration of j, you write over all of the C matrix, so at the end, C is just going to be the result of executing the last i and last j

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Answer 1

Image Analyst 2018-1-24

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/378666-i-have-an-image-and-i-need-to-extract-local-features-so-i-divided-it-to-16-blocks-and-size-of-each-b#answer_301464

在 MATLAB Online 中打开

Try

k = 1;
for i=1:(r/bs)
    for j=1:(c/bs)
         % code snipped....
         C{k} = imcrop(a,[col1 row1 col2 row2]);   
         k = k + 1;
    end
end

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teja jayavarapu 2018-1-24

I have tried that way it works,but when quantification is done we will get 16 different values of X how to store those X values such as (X1,X2..) in G

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