[HELP] Extract double array from cell

I have an image which has been divided into 49 blocks. from the block I would like to get the feature vector of LBP from each cell. what can i do?

any advise is greatly appreciated.

 proceed = 1;
 data_matrix = [];
 ids = [];
 conut = 0;
 l=0;

 for i=1:100
        for j=1:10

 s = sprintf('database/s%i/%i.jpg',i,j);
           X = double(imread(s));

            [rows columns] = size(X);
            blockSizeR = 45; % Rows in block.
            blockSizeC = 34; % Columns in block.
          % Figure out the size of each block in rows. 
% Most will be blockSizeR but there may be a remainder amount of less than that.
            wholeBlockRows = floor(rows / blockSizeR);
            blockVectorR = [blockSizeR * ones(1, wholeBlockRows), rem(rows, blockSizeR)];
% Figure out the size of each block in columns. 
            wholeBlockCols = floor(columns / blockSizeC);
            blockVectorC = [blockSizeC * ones(1, wholeBlockCols), rem(columns, blockSizeC)];
% Dividing the image into 49 Blocks
                ca = mat2cell(X, blockVectorR, blockVectorC);
                eval(['out_' num2str(l) '=ca' ]);
                l=l+1;

              MAPPING=getmapping(8,'riu2');

             feature_vector = lbp(ca,1,8,MAPPING,'hist');
            feat_vect=feature_vector';
            data_matrix = [data_matrix,feat_vect];

        end 
end

[Guillaume]

What is the problem with the code you've written? Doesn't it do what you're asking?

[Seprienna]

it suppose to work, but I couldn't get the new input image to be working. any advise. i'm getting this error'Conversion to double from cell is not possible.

Answer 1

[Guillaume]

I'm assuming that the lbp code you're referring to is from http://www.cse.oulu.fi/CMV/Downloads/LBPMatlab, which would indeed give you the error you mention if you pass it the cell array ca since it is expecting an image.

Possibly, what you want to do is:

feature_vectors = cellfun(@(cell) lbp(cell, 1, 8, MAPPING, 'hist'), ca, 'UniformOutput', false);

which will send each cell in turn to lbp and collate all the returned values in a cell array.

If you want to then stuff these return values in your data_matrix you'll have to change its declaration to:

data_matrix = {}; %cell array instead of matrix

and concatenate it with

data_matrix = [data_matrix {feature_vectors}];

or you could just do

data_matrix{l} = feature_vectors;

[Seprienna]

thank you very much..very helpful information. and yes that the standard lbp code i'm using.