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Convert binary image to rgb image again ?is it possible?

Asked by I Made on 20 Mar 2013

I'm trying to convert rgb image to binary image using code i found on this website too :

    Irgb = imread('wtmk.png');
    threshold = 128; 
    Igray = rgb2gray(Irgb); 
    Ibw = Igray>threshold;

I wonder if i can get back to rgb image from binary image? anyone can give me advise?

0 Comments

I Made

2 Answers

Answer by Image Analyst on 20 Mar 2013

Do you want a watermarking demo, because I can give that to you for gray scale images? For color, you simply extract the 3 color channels:

redChannel = rgbImage(:, :, 1); greenChannel = rgbImage(:, :, 2); blueChannel = rgbImage(:, :, 3);

watermark each of the three color channels individually, and then recombine with cat:

watermarkedRGBImage = cat(3, watermarkedRed, watermarkedRGreen, watermarkedRBlue);

at least that's one way - I'm sure there are more sophisticated methods with hidden watermarks that are more resistant to attack (cropping, rotating, adding noise, etc.).

3 Comments

I Made on 21 Mar 2013

Yes please sir, maybe demo could help

Image Analyst on 21 Mar 2013
% 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.
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;
	end
end
originalImage = 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;
	end
end
hiddenImage = 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 = {'6'};
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; % Initialize
for column = 1 : visibleColumns
	for row = 1 : visibleRows
		watermarkedImage(row, column) = bitset(originalImage(row, column), bitToSet, watermark(row, column));
	end
end
% 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', 0, 0.0005);
% 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);
	end
end
% 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!');
I Made on 21 Mar 2013

Thank you sir, but i need time to learn it.

Image Analyst
Answer by Wouter on 20 Mar 2013
Edited by Wouter on 20 Mar 2013

You can create a masked RGB image from the Ibw and Irgb images; by using:

 Irgb_new = Irgb;
 Irgb_new(~repmat((Ibw),[1 1 3])) = 0

You cannot retrieve the orginal rgb values from just Ibw.

5 Comments

I Made on 20 Mar 2013

Yes that what was i'm thinking, so i need to insert additional information to the signal right? i currently only inserting information in binary form, that's why i try to convert the rgb image to binary but then stuck when trying to convert it back.

Wouter on 20 Mar 2013

Why don't you just insert the entire RGB image?

I Made on 21 Mar 2013

My method of inserting it only can work in binary.. and i think it's to big too..

Wouter

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