how to embed a watermark in the centre of an image?

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shafaq innam
shafaq innam on 3 Apr 2013
i have embedded the watermark in the the four corners by using the code
m((size(m,1)-size(n,1)+1):end, (size(m,2)-size(n,2)+1):end,1:end) = n;
plz tell me the way to replace the pixels of an image by another so that i can embed the watermark anywhere..

Answers (1)

Image Analyst
Image Analyst on 3 Apr 2013
Here's a demo for replacing pixels in an image with another image.
% Lets user drag out a box on an image, then define where they want to paste it.
% Then is pastes the drawn region onto the original image.
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;
format compact;
% Check that user has the Image Processing Toolbox installed.
hasIPT = license('test', 'image_toolbox');
if ~hasIPT
% User does not have the toolbox installed.
message = sprintf('Sorry, but you do not seem to have the Image Processing Toolbox.\nDo you want to try to continue anyway?');
reply = questdlg(message, 'Toolbox missing', 'Yes', 'No', 'Yes');
if strcmpi(reply, 'No')
% User said No, so exit.
% Read in a standard MATLAB gray scale demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
baseFileName = 'eight.tif';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
% File doesn't exist -- 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 in the search path folders.', fullFileName);
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);
axis on;
title('Original Grayscale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Give a name to the title bar.
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off')
% Let's compute and display the histogram, just for fun.
[pixelCount grayLevels] = imhist(grayImage);
subplot(2, 2, 2);
grid on;
title('Histogram of original image', 'FontSize', fontSize);
xlim([0 grayLevels(end)]); % Scale x axis manually.
% Ask user to draw a box.
subplot(2, 2, 1);
promptMessage = sprintf('Drag out a box that you want to copy,\nor click Cancel to quit.');
titleBarCaption = 'Continue?';
button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
if strcmpi(button, 'Cancel')
k = waitforbuttonpress;
point1 = get(gca,'CurrentPoint'); % button down detected
finalRect = rbbox; % return figure units
point2 = get(gca,'CurrentPoint'); % button up detected
point1 = point1(1,1:2); % extract x and y
point2 = point2(1,1:2);
p1 = min(point1,point2); % calculate locations
offset = abs(point1-point2); % and dimensions
% Find the coordinates of the box.
xCoords = [p1(1) p1(1)+offset(1) p1(1)+offset(1) p1(1) p1(1)];
yCoords = [p1(2) p1(2) p1(2)+offset(2) p1(2)+offset(2) p1(2)];
x1 = round(xCoords(1));
x2 = round(xCoords(2));
y1 = round(yCoords(5));
y2 = round(yCoords(3));
hold on
axis manual
plot(xCoords, yCoords, 'b-'); % redraw in dataspace units
% Display the cropped image.
croppedImage = grayImage(y1:y2,x1:x2);
subplot(2, 2, 3);
axis on;
title('Region that you defined', 'FontSize', fontSize);
% Paste it onto the original image
[rows2 columns2] = size(croppedImage)
promptMessage = sprintf('Click on the upper left point where you want to paste it,\nor click Cancel to quit.');
titleBarCaption = 'Continue?';
button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
if strcmpi(button, 'Cancel')
[x, y] = ginput(1)
% Determine the pasting boundaries.
r1 = int32(y);
c1 = int32(x);
r2 = r1 + rows2 - 1;
r2 = min([r2 rows]);
c2 = c1 + columns2 - 1;
c2 = min([c2, columns]);
plot([c1 c2 c2 c1 c1], [r1 r1 r2 r2 r1], 'r-');
% Paste as much of croppedImage as will fit into the original image.
grayImage(r1:r2, c1:c2) = croppedImage(1:(r2-r1+1), 1:(c2-c1+1));
subplot(2, 2, 4);
axis on;
title('Region that you defined pasted onto original', 'FontSize', fontSize);
Image Analyst
Image Analyst on 8 Apr 2013
Look how I calculate r1,r2,c1,c2. You can figure them out knowing the size of your image, right? Like
r1 = floor((bigImageRows - smallImageRows)/2);
r2 = r1 + smallImageRows - 1;
c1 = floor((bigImageCols - smallImageCols)/2);
c2 = r1 + smallImageCols - 1;
grayImage(r1:r2, c1:c2) = smallImage;
or something like that. It's just simple algebra - you can do it, I'm sure.

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