If suppose the number is 110110, how to get its LSB in matlab?
MATLAB: How to get the LSB of a number
lsb
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If you simply want to get a bit-stream representation, it does not matter in any way, if the data are a wav file or a jpeg. A WAV file contains additional header information compared to the pure signal. Getting a bit-stream from it:
fid = fopen(FileName, 'r');data = fread(fid, [1, Inf], 'uint8');fclose(fid);bit = uint8(rem(floor((1 ./ [128, 64, 32, 16, 8, 4, 2, 1].') * data), 2));bit = bit(:);Now you have a bit stream of 1s and 0s stored in an UINT8 vector. This contains the complete data of the file and does not care in any way about the contents or format.
Well here's my demo. It lets you hide an watermark image, which may be bigger or smaller than a cover image, into a user-specified bitplane of the cover (original) image. If the watermark is bigger than the original image, it scales it down. If the watermark is smaller, it tiles it. The watermark image can be grayscale and you can specify where you want it thresholded at. It uses standard MATLAB demo images. If the images are color, it takes the red channel - I haven't made it to work with color images. At the end it adds noise and recovers the watermark from the noise-free and noisy images, so you can see how lousy this method is as far as being robust to attack.
% Demo to watermark an image by hiding another image in a certain bit
% plane. Sometimes called "LSB Watermarking" or something similar.
% User is asked which bit plane they want to hide the image in.
% By Image Analyst.
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 = 12;% Read in the image what will have another image hidden into it.
baseFileName='moon.tif';% baseFileName='cameraman.tif';
folder = fullfile(matlabroot, '\toolbox\images\imdemos');% 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; endendoriginalImage = imread(fullFileName);% Get the number of rows and columns in the original image.
[visibleRows visibleColumns numberOfColorChannels] = size(originalImage);if numberOfColorChannels > 1 % If it's color, extract the red channel.
originalImage = originalImage(:,:,1);end% Display the original gray scale image.
subplot(3, 3, 4);imshow(originalImage, []);title('Original Grayscale Starting Image', 'FontSize', fontSize);% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);set(gcf,'name','Demo by ImageAnalyst','numbertitle','off') % read the message image you want to hide in the cover image
baseFileName='cameraman.tif';% baseFileName='moon.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; endendhiddenImage = imread(fullFileName);% Get the number of rows and columns in the hidden image.
[hiddenRows hiddenColumns numberOfColorChannels] = size(hiddenImage);if numberOfColorChannels > 1 % If it's color, extract the red channel. hiddenImage = hiddenImage(:,:,1);end% Display the image.
subplot(3, 3, 1);imshow(hiddenImage, []);title('Image to be Hidden', 'FontSize', fontSize);% Let's compute and display the histogram.
[pixelCount grayLevels] = imhist(hiddenImage);subplot(3, 3, 2); bar(pixelCount);title('Histogram of image to be hidden', 'FontSize', fontSize);xlim([0 grayLevels(end)]); % Scale x axis manually.
grid on;thresholdValue = 70;binaryImage = hiddenImage < thresholdValue;% Display the image.subplot(3, 3, 3);imshow(binaryImage, []);caption = sprintf('Hidden Image Thresholded at %d', thresholdValue);title(caption, 'FontSize', fontSize);% Get the bit plane to hide the image in.
prompt = 'Enter the bit plane you want to hide the image in (1 - 8) ';dialogTitle = 'Enter Bit Plane to Replace';numberOfLines = 1;defaultResponse = {'1'};bitToSet = str2double(cell2mat(inputdlg(prompt, dialogTitle, numberOfLines, defaultResponse)));% If image to be hidden is bigger than the original image, scale it down.
if hiddenRows > visibleRows || hiddenColumns > visibleColumns amountToShrink = min([visibleRows / hiddenRows, visibleColumns / hiddenColumns]); binaryImage = imresize(binaryImage, amountToShrink); % Need to update the number of rows and columns.
[hiddenRows hiddenColumns] = size(binaryImage);end% Tile the hiddenImage, if it's smaller, so that it will cover the original image.
if hiddenRows < visibleRows || hiddenColumns < visibleColumns watermark = zeros(size(originalImage), 'uint8'); for column = 1:visibleColumns for row = 1:visibleRows watermark(row, column) = binaryImage(mod(row,hiddenRows)+1, mod(column,hiddenColumns)+1); end end % Crop it to the same size as the original image.
watermark = watermark(1:visibleRows, 1:visibleColumns);else % Watermark is the same size as the original image.
watermark = binaryImage;end% Display the thresholded binary image - the watermark alone.
subplot(3, 3, 5);imshow(watermark, []);caption = sprintf('Hidden Image\nto be Inserted into Bit Plane %d', bitToSet);title(caption, 'FontSize', fontSize);% Set the bit of originalImage(a copy, actually) to the value of the watermark.
watermarkedImage=originalImage;for column = 1:visibleColumns for row = 1:visibleRows watermarkedImage(row, column)=bitset(originalImage(row, column), bitToSet, watermark(row, column)); endend% Display the image.subplot(3, 3, 6);imshow(watermarkedImage, []);caption = sprintf('Final Watermarked Image\nwithout added Noise');title(caption, 'FontSize', fontSize);% add noise to watermarked image
noisyWatermarkedImage = imnoise(watermarkedImage,'gaussian');% Display the image.subplot(3, 3, 7);imshow(noisyWatermarkedImage, []);caption = sprintf('Watermarked Image\nwith added Noise');title(caption, 'FontSize', fontSize);%====================================================================================
% Now let's pretend we are starting with the watermarked noisy corrupted image.
% We want to recover the watermark.
% Use the known bitplane of watermarked image to recover the watermark.
recoveredWatermark = zeros(size(noisyWatermarkedImage));recoveredNoisyWatermark = zeros(size(noisyWatermarkedImage));for column = 1:visibleColumns for row = 1:visibleRows recoveredWatermark(row, column) = bitget(watermarkedImage(row, column), bitToSet); recoveredNoisyWatermark(row, column) = bitget(noisyWatermarkedImage(row, column), bitToSet); endend% Scale the recovered watermark to 0=255
recoveredWatermark = uint8(255 * recoveredWatermark);recoveredNoisyWatermark = uint8(255 * recoveredNoisyWatermark);% Display the images.
subplot(3, 3, 8);imshow(recoveredWatermark, []);caption = sprintf('Watermark Recovered\nfrom Bit Plane %d of\nNoise-Free Watermarked Image', bitToSet);title(caption, 'FontSize', fontSize);% Display the images.subplot(3, 3, 9);imshow(recoveredNoisyWatermark, []);caption = sprintf('Watermark Recovered\nfrom Bit Plane %d of\nNoisy Watermarked Image', bitToSet);title(caption, 'FontSize', fontSize);msgbox('Done with demo!');
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