How to read RGB values from each block after running this code?

Question

ARNABJIT CHOUDHURY 2021-5-20

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/835603-how-to-read-rgb-values-from-each-block-after-running-this-code

评论： Sulaymon Eshkabilov 2021-5-21

I have written a code for segment an image into 12 blocks.

clear; clc;
i=imread('./train/aa.png');
i2=imresize(i,[400,300]);
[rows columns numberOfColorBands] = size(i2);
%divide image up into blocks
blockSizeR = 100; %Rows in block
blockSizeC = 100; %Columns in block
 %Figure out the size of each block in rows.
wholeBlockRows = floor(rows / blockSizeR);
blockVectorR = [blockSizeR * ones(1, wholeBlockRows)];
% Figure out the size of each block in columns.
wholeBlockCols = floor(columns / blockSizeC);
blockVectorC = [blockSizeC * ones(1, wholeBlockCols)];
% Create the cell array, ca.  
% in the array contains a blockSizeR by blockSizeC by 3 color array.
% This line is where the image is actually divided up into blocks.
if numberOfColorBands > 1
  % It's a color image.
  ca = mat2cell(i2, blockVectorR, blockVectorC, numberOfColorBands);
else
  ca = mat2cell(i2, blockVectorR, blockVectorC);
end
% Now display all the blocks.
plotIndex = 1;
numPlotsR = size(ca, 1);
numPlotsC = size(ca, 2);
for r = 1 : numPlotsR
  for c = 1 : numPlotsC
    fprintf('plotindex = %d,   c=%d, r=%d\n', plotIndex, c, r);
    % Specify the location for display of the image.
    subplot(numPlotsR, numPlotsC, plotIndex);
    % Extract the numerical array out of the cell
    % just for tutorial purposes.
    rgbBlock = ca{r,c};
    imshow(rgbBlock); % Could call imshow(ca{r,c}) if you wanted to.
    [rowsB columnsB numberOfColorBandsB] = size(rgbBlock);
    % Make the caption the block number.
    caption = sprintf('Block #%d of %d\n%d rows by %d columns', ...
      plotIndex, numPlotsR*numPlotsC, rowsB, columnsB);
    title(caption);
    drawnow;
    % Increment the subplot to the next location.
    plotIndex = plotIndex + 1;
  end
end

Now,I want to read the RGB values from each block and calculate their mean and standard deviation and make a 72 element feature vector that would be feeded in to the feature vector storage. Please help. I need to submit the project. Thank you very much.

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Answer 1

Sulaymon Eshkabilov 2021-5-20

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/835603-how-to-read-rgb-values-from-each-block-after-running-this-code#answer_704893

在 MATLAB Online 中打开

Here are the calculations missing in your code to compute mean, std of R, G, B, etc.

... 
% just for tutorial purposes.
    rgbBlock = ca{r,c};
    R{plotIndex}=rgbBlock(:,:,1);  % Red
    B{plotIndex}=rgbBlock(:,:,2);  % Green
    B{plotIndex}=rgbBlock(:,:,3);  % Blue
    R_Mean(plotIndex) = mean2(rgbBlock(:,:,1)); % Mean of Red
    G_Mean(plotIndex) = mean2(rgbBlock(:,:,2)); % Mean of Green
    B_Mean(plotIndex) = mean2(rgbBlock(:,:,3)); % Mean of Blue
    STD_R(plotIndex)=std(double(rgbBlock(:,:,1)), 0, 'all');
    STD_G(plotIndex)=std(double(rgbBlock(:,:,2)), 0, 'all');
    STD_B(plotIndex)=std(double(rgbBlock(:,:,3)), 0, 'all');
    imshow(rgbBlock); % Could call imshow(ca{r,c}) if you wanted to.
    ...
        