Saving an image in a for loop with an index

Hi there,

I am very new to coding so please excuse any ignorance - i am learing. My objective is to get an image, split it into a grid, and then save each grid into a folder. I have been successful for most of it except saving each grid into a folder. I can only save the first grid that i have produced. I need to be able to save every block from my grid into the folder and assign it a unique index. Can anyone help please? Here is my code:

thank you so much

% 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('B#%d', ...

plotIndex, numPlotsR*numPlotsC, rowsB, columnsB);

title(caption);

          drawnow;
          % Increment the subplot to the next location.
            %%saving to new directory for processing in CNN
          imwrite (rgbBlock, 'Z:\Aerial Images\Images\Output1.jpg', 'jpg');

          plotIndex = plotIndex + 1;
      end
  end

Answer 1

[Walter Roberson]

projectdir = 'Z:\Aerial Images\Images';

% 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('B#%d', ...

plotIndex, numPlotsR*numPlotsC, rowsB, columnsB);

title(caption);

            drawnow;
            % Increment the subplot to the next location.
              %%saving to new directory for processing in CNN
            filename = fullfile(projectdir, 'Output%03d_%03d.jpg', r, c);;
            imwrite(rgbBlock, filename);
            plotIndex = plotIndex + 1;
        end
    end

[Zachary Gancarz]

didn't seem to work. here is my full code and a pic of the image i'm splitting and the output in my folder, the pictures 1 to 10 are all of the bottom right grid (hard to see but need to zoom).. thank you!!

% Demo to divide an image up into blocks (non-overlapping tiles).
% The first way to divide an image up into blocks is by using mat2cell().
% In this demo, I demonstrate that with a color image.
% Another way to split the image up into blocks is to use indexing.
% In this demo, I demonstrate that method with a grayscale image.

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
workspace;  % Make sure the workspace panel is showing.
fontSize = 20;

% Read in a standard MATLAB color demo image.
folder = fullfile('Z:\Aerial Images');
%baseFileName = 'ecw.jp2';
baseFileName = 'IMG_5181.jpg';

% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
if ~exist(fullFileName, 'file')
    % Didn't find it there.  Check the search path for it.
    fullFileName = baseFileName; % No path this time.
    if ~exist(fullFileName, 'file')
        % Still didn't find it.  Alert user.
        errorMessage = sprintf('Error: %s does not exist.', fullFileName);
        uiwait(warndlg(errorMessage));
        return;
    end
end
% Read the image from disk + show info about the image

rgbImage = imread(fullFileName);

imshow (rgbImage)

% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
drawnow;
% Get the dimensions of the image.  numberOfColorBands should be = 3.
[rows columns numberOfColorBands] = size(rgbImage)

%==========================================================================
% The first way to divide an image up into blocks is by using mat2cell().
blockSizeR = 500; % Rows in block.
blockSizeC = 500; % Columns in block.

wholeBlockRows = floor(rows / blockSizeR);
blockVectorR = [blockSizeR * ones(1, wholeBlockRows), rem(rows, blockSizeR)];

wholeBlockCols = floor(columns / blockSizeC);
blockVectorC = [blockSizeC * ones(1, wholeBlockCols), rem(columns, blockSizeC)];

if numberOfColorBands > 1
    % It's a color image.
    ca = mat2cell(rgbImage, blockVectorR, blockVectorC, numberOfColorBands);
else
    ca = mat2cell(rgbImage, 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);

          drawnow;

          plotIndex = plotIndex + 1;

      end

end
              N = 1;
A = rgbBlock;
for ii = 1:10   
   imwrite(A,strcat('Z:/Aerial Images/Images/',num2str(ii),'.jpg'));

end

[Image Analyst]

Use A{ii} in imwrite.

[Zachary Gancarz]

Thanks for the help IA, it seems to save it as a 1x1 pixel now. Any ideas?

Cheers

[Image Analyst]

rgbBlock is just a single image that gets overwritten every single iteration and so after the two loops, it will be the last image. So you can't have another loop outside the first pair since there's no use - A will be just one single image, not a cell array of images. I recommend that, if you want to save each image block, to put the imwrite() inside your loop over c.

[Zachary Gancarz]

thanks brother

Answer 2

[Zachary Gancarz]

Anyone have an idea? I'm getting blank 1x1 pixels. Can't seem to figure it out

cheers