I have to resize my image to a fix size of 256*256 and then I have to divide the image into two 2*2 non overlapping blocks? i have made this code but its not working on my image

img=imread('cameraman.tif');
[m n]=size(img);

block=4;
%slide_len=1;

for ix=0:block:m-block
    for jy=0:block:n-block
        current_block=img((ix+1):(ix+block),(jy+1):(jy+block));
        dct_coeff((ix+1):(ix+block),(jy+1):(jy+block))=current_block;

      end
  end
  subplot(2,1,1)
  imshow(dct_coeff);
  fun=@dct2;
  c=blkproc(img,[4 4],fun);
  subplot(2,1,2)
  imshow(c);

Answer 1

[Image Analyst]

image256x256 = imresize(img, [256, 256]);

See if the FAQ helps you with blockproc(): http://matlab.wikia.com/wiki/FAQ#How_do_I_split_an_image_into_non-overlapping_blocks.3F

Answer 2

[Ranu Bhardwaj]

img_Folder = fullfile(matlabroot, '\toolbox\images\imdemos');

F1 = 'cameraman.tif';

F1_name = fullfile(img_Folder, F1); %#ok<NASGU>

if ~exist(F1_name, 'file')

    F1_name = F1; % No path this time.
    if ~exist(F1_name, 'file')
        errormsg = sprintf('Error: %s does not exist.', F1_name);
        uiwait(warndlg(errormsg));
        return;
    end
end
grayimg = imread(F1_name);
[rows columns numberOfColorBands] = size(grayimg); %#ok<NCOMMA>
figure;
subplot(2, 2, 1);
imshow(grayimg, []);fontSize=10;
title('Original Grayscale Image', 'FontSize', fontSize);
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
blockSizeR = 128; % Rows in block.
blockSizeC = 128; % Columns in block.
wholeBlockRows = floor(rows / blockSizeR);
wholeBlockCols = floor(columns / blockSizeC);
image3d = zeros(wholeBlockRows, wholeBlockCols, 3);
img = 1;
for row = 1 : blockSizeR : rows
    for col = 1 : blockSizeC : columns
        row1 = row;
        row2 = row1 + blockSizeR - 1;
        row2 = min(rows, row2); % Don't let it go outside the image.
        col1 = col;
        col2 = col1 + blockSizeC - 1;
        col2 = min(columns, col2); % Don't let it go outside the image.
        First_img = grayimg(row1:row2, col1:col2);
        subplot(2, 2, img);
        imshow(First_img);
        drawnow;
        if (row2-row1+1) == blockSizeR && (col2-col1+1) == blockSizeC
            image3D(:, :, img) = First_img; %#ok<SAGROW>
        else
            Blocl = [(row2-row1+1), (col2-col1+1)];
            warningMessage = sprintf('Warning: this block size of %d rows and %d columns\ndoes not match the preset block size of %d rows and %d columns.\nIt will not be added to the 3D image stack.',...
                Blocl(1), Blocl(2), blockSizeR, blockSizeC);
            uiwait(warndlg(warningMessage));
        end
        img = img + 1;
    end
end