y i m getting Subscripted assignment dimension mismatch error?

 clear all
clc
a=imread('vc1.gif');
a=double(a);
r=input('which bit image do you want to see 1=MSB 8=LSB');
[row col]=size(a);
for x=1:1:row
for y=1:1:col
    c=dec2bin(a(x,y),8);
    d=c(r);
    w(x,y)=double(d);
    if w(x,y)==49
        w(x,y)=255;
    else
        w(x,y)=0;
    end
end
end
figure(1)
imshow(uint8(a))
figure(2)
imshow(uint8(w))

[Image Analyst]

Instead of that whole long, inefficient double for loop, you really only need one line:

bitPlaneImage = bitand(grayImage, 2^bp);

See how I do it in my full-blown demo below.

Answer 1

[Wayne King]

I do not have trouble running this code with the following (although I get a display warning at the end)

 a = imread('ngc6543a.jpg');

Can you please indicate what the size of a is after your call to imread()

Answer 2

[Image Analyst]

Even though that might seem intuitive, that's an inefficient way to do it. Here, try it my way - run my demo:

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

% Read in a standard MATLAB gray scale demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
baseFileName = 'cameraman.tif';
% 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
grayImage = imread(fullFileName);
% Get the dimensions of the image.  numberOfColorBands should be = 1.
[rows columns numberOfColorBands] = size(grayImage);
% Display the original gray scale image.
subplot(2, 2, 1);
imshow(grayImage, []);
title('Original Grayscale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'Position', get(0,'Screensize')); 

% Let's compute and display the histogram.
[pixelCount grayLevels] = imhist(grayImage);
subplot(2, 2, 2); 
bar(pixelCount);
grid on;
title('Histogram of Original Grayscale Image', 'FontSize', fontSize);
xlim([0 grayLevels(end)]); % Scale x axis manually.
% Let's use this spot for the output image.
subplot(2, 3, 5); 

for bp = 0 : 7
    % Compute the bit plane image.
    bitPlaneImage = bitand(grayImage, 2^bp);
    % Display it as pure black and white (not gray scale).
    imshow(bitPlaneImage, []);
    caption =  sprintf('You are now viewing bitplane %d.', bp);
    title(caption, 'FontSize', fontSize);

      % If it's not the last bit plane, ask them if they want to continue.
      if bp ~= 7
          message = sprintf('%s\nDo you want to continue', caption);
          button = questdlg(message, 'Continue?', 'Yes', 'No', 'Yes');
          drawnow;  % Refresh screen to get rid of dialog box remnants.
          if strcmpi(button, 'No')
             break;
          end
      end
  end

msgbox('Done with demo');