How to change color in overlapping image ?

I created an overlapping image from two images, a and b; I get green-magenta colors:

I want to control the color output: for example, I want blue and red.

      c=imfuse(a,b,'falsecolr','Scaling','joint');

All suggestions are welcome

Answer 1

[Image Analyst]

You can use cat(3, r, g, b) to combine images into any color channels you want.

[Bruno]

Thanks for your answer, can you expand on cat(3, r, g, b)?

[Bruno]

 I tried to obtain blue and red colors; I'm not winning

   c=imfuse(a,b,'falsecolr','Scaling','joint');
   redChannel = c(:, :, 1);
   greenChannel = c(:, :, 2);
   blueChannel = c(:, :, 3);
   rgbImage = cat(2,redChannel,blueChannel);
   imshow (rgbImage)

[Image Analyst]

the (badly-named) a and b are gray scale images, correct? If so what color channel do you want a to go into and what color channel do you want b to go into? Don't use imfuse and if you want a to be red, nothing to be green, and b to be blue, do this:

blackImage = zeros(size(a), class(a));
rgbImage = cat(3, a, blackImage, b);

[Bruno]

I really appreciate your help, next time I will use better name;

a and b are black and the background is white, it's not working

[Image Analyst]

Can you answer my second question? And attach a and b because there is no way you can overlap two black images and get magenta. I'll check back in a couple of hours.

[Bruno]

I want red for a and blue for b (you are right are badly named).

The images contain a stick figure (in black) with white background; when I overlapped the two images and I get a white background and the overlap stick figures are green, magenta and black (similar).

[Image Analyst]

If you want "red for a and blue for b" and a and b are both all black, then you're gong to have to change them to something non-black if you want them to have values in the red and blue channels, otherwise you'll just end up with black again. See how much including the images can help us learn what you want to do? Unfortunately, you forgot again to attach the images. What color(s) do you want the stick figures? Both the same color or different colors? And the white background - should it stay white, or be some other color? For it to stay white, you're going to have to have a third channel with stick figures on it. I'll check back later, maybe tomorrow.

[Bruno]

I attached the image: I overlapped image1 and image2 with imfuse;

Now the color of Overlap-Image is green-magenta (by Default imfuse uses this colors) I want it to be red-blue.

Image Analyst, I truly appreciate your help

[Image Analyst]

Can you post image1 and image2 as separate figures so I don't have to split them apart at some guessed column?

[Bruno]

Hi, I attached the two images as png files.

[Bruno]

Did you receive the images?

[Image Analyst]

Try this:

clc;  % Clear command window.
clear;  % Delete all variables.
close all;  % Close all figure windows except those created by imtool.
workspace;  % Make sure the workspace panel is showing.
fontSize = 20;

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;

% Check that user has the specified Toolbox installed and licensed.
hasLicenseForToolbox = license('test', 'image_toolbox');   % license('test','Statistics_toolbox'), license('test','Signal_toolbox')
if ~hasLicenseForToolbox
  % User does not have the toolbox installed, or if it is, there is no available license for it.
  % For example, there is a pool of 10 licenses and all 10 have been checked out by other people already.
  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.
    return;
  end
end

%===============================================================================
% Read in a first gray scale demo image.
folder = pwd;
baseFileName = 'frame0017.png';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
  % The file doesn't exist -- didn't find it there in that folder.
  % Check the entire search path (other folders) for the file by stripping off the folder.
  fullFileNameOnSearchPath = baseFileName; % No path this time.
  if ~exist(fullFileNameOnSearchPath, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
grayImage1 = imread(fullFileName);
% Get the dimensions of the image.
% numberOfColorChannels should be = 1 for a gray scale image, and 3 for an RGB color image.
[rows, columns, numberOfColorChannels] = size(grayImage1);
if numberOfColorChannels > 1
  % It's not really gray scale like we expected - it's color.
  % Use weighted sum of ALL channels to create a gray scale image.
  grayImage1 = rgb2gray(grayImage1);
  % ALTERNATE METHOD: Convert it to gray scale by taking only the green channel,
  % which in a typical snapshot will be the least noisy channel.
  % grayImage = grayImage(:, :, 2); % Take green channel.
end
% Display the image.
subplot(2, 3, 1);
imshow(grayImage1, []);
title('Gray Image 1', 'FontSize', fontSize, 'Interpreter', 'None');

% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0, 0, 1, 1]);
% Get rid of tool bar and pulldown menus that are along top of figure.
% set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')

% Threshold the image.
binaryImage1 = grayImage1 < 128;
% Display the image.
subplot(2, 3, 4);
imshow(binaryImage1, []);
title('Binary Image 1', 'FontSize', fontSize, 'Interpreter', 'None');

%===============================================================================
% Read in a second gray scale demo image.
folder = pwd;
baseFileName = 'frame0031.png';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
  % The file doesn't exist -- didn't find it there in that folder.
  % Check the entire search path (other folders) for the file by stripping off the folder.
  fullFileNameOnSearchPath = baseFileName; % No path this time.
  if ~exist(fullFileNameOnSearchPath, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
grayImage2 = imread(fullFileName);
% Get the dimensions of the image.
% numberOfColorChannels should be = 1 for a gray scale image, and 3 for an RGB color image.
[rows, columns, numberOfColorChannels] = size(grayImage2);
if numberOfColorChannels > 1
  % It's not really gray scale like we expected - it's color.
  % Use weighted sum of ALL channels to create a gray scale image.
  grayImage2 = rgb2gray(grayImage2);
  % ALTERNATE METHOD: Convert it to gray scale by taking only the green channel,
  % which in a typical snapshot will be the least noisy channel.
  % grayImage = grayImage(:, :, 2); % Take green channel.
end
% Display the image.
subplot(2, 3, 2);
imshow(grayImage2, []);
title('Gray Image 2', 'FontSize', fontSize, 'Interpreter', 'None');

% Threshold the image.
binaryImage2 = grayImage2 < 128;
% Display the image.
subplot(2, 3, 5);
imshow(binaryImage2, []);
title('Binary Image 2', 'FontSize', fontSize, 'Interpreter', 'None');

% Find out where they match
matching = binaryImage1 & binaryImage2;

% Make black image
blackImage = zeros(size(binaryImage1), 'uint8');

% Put binaryImage1 into red channel and binaryImage2 into blue channel
rgbImage = cat(3, uint8(binaryImage1), blackImage, uint8(binaryImage2));
% Make uint8 RGB
rgbImage = uint8(255 * rgbImage);
% Make black background white.
blackMask = ~binaryImage1 & ~binaryImage2;
blackMask = uint8(255 *cat(3, blackMask, blackMask, blackMask)); % Make color.
% Mask the image using bsxfun() function
rgbImage = blackMask + rgbImage;
% Display the image.
subplot(2, 3, 6);
imshow(rgbImage, []);
title('Final Color Image', 'FontSize', fontSize, 'Interpreter', 'None');

[Bruno]

nice, it is perfect

I really appreciate your help

[Image Analyst]

You're welcome - thanks for Accepting. Actually you don't need this line

matching = binaryImage1 & binaryImage2;

I ended up not using it.

[Bruno]

Okay,

Great Code

Answer 2

[Saif]

how we change background color into logo colour and logo into backgorund color white and green

[DGM]

Please open a new question for this by clicking Ask at the top of the page. When you do, make sure to provide example images for context and explain specifically which parts of which image(s) should be a particular color.

Answer 3

[DGM]

Imfuse() does support channel specification. That may suffice in some cases.

% read the files
frame1 = imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/83841/frame0017.png');
frame2 = imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/83840/frame0031.png');

% one line
outpict = imfuse(frame1,frame2,'colorchannels',[1 0 2]);

imshow(outpict)

Of course, these images are negative (black-on-white), so it's confusing. The object colors are actually swapped because the black regions are colored by the background of the opposite image. It would be a lot simpler to just invert the source images.

% invert sources for less confusion
frame1 = imcomplement(frame1);
frame2 = imcomplement(frame2);

outpict = imfuse(frame1,frame2,'colorchannels',[1 0 2]);

imshow(outpict)

Note that this does not require any information to be lost in binarization, and it still allows the use of other features of imfuse().

Now let's say you wanted the background to stay white. For this simple diagram, the object polarity seems almost arbitrary, but let's consider a different set of sources.

frame1 = imread('cameraman.tif');
frame2 = fliplr(frame1);

frame1 = imcomplement(frame1);
frame2 = imcomplement(frame2);

outpict = imfuse(frame1,frame2,'colorchannels',[1 0 2]);

imshow(outpict)

In this case, we have images where the primary object content is obviously supposed to be dark-on-light. It's also plausible that we wouldn't want to binarize the sources.

This is an extra complication that really can't be solved with imfuse() directly. One might think that the current output could simply be inverted, but that would require specifying that the image colors are yellow and cyan -- and we can't specify two secondary colors. Not only does imfuse() not allow it, we'd be losing a lot of color mixing if we did.

One way to deal with the problem is by doing a lightness inversion on the output. If you have the tools, this adds only one line.

frame1 = imread('cameraman.tif');
frame2 = fliplr(frame1);

frame1 = imcomplement(frame1);
frame2 = imcomplement(frame2);

outpict = imfuse(frame1,frame2,'colorchannels',[1 0 2]);

% invert L
outpict = imtweak(outpict,'hsl',[0 1 -1]);

imshow(outpict)

Now the primary object in frame1 appears red and in the appropriate polarity. The same can be applied to the original images:

frame1 = imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/83841/frame0017.png');
frame2 = imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/83840/frame0031.png');

frame1 = imcomplement(frame1);
frame2 = imcomplement(frame2);

outpict = imfuse(frame1,frame2,'colorchannels',[1 0 2]);

% invert L
outpict = imtweak(outpict,'hsl',[0 1 -1]);

imshow(outpict)

Note that this transformation works in HSL, but not in HSV. Base MATLAB/IPT do not have HSL conversion tools, so I'm using imtweak() from MIMT to do the adjustment.

Personally, I'd rather avoid the confusion and stay with light-on-dark polarity, as it makes it easier to visually understand the contributions from each image. It's my opinion that having the images in the original polarity is unimportant when treating imfuse() simply as a visual comparison tool.

[DGM]

I mentioned that we'd lose some color mixing if we tried to do the blending using two secondary-color images. Here's an example of what would happen. First, let's consider the case with a continuous image.

frame1 = imread('cameraman.tif');
frame2 = fliplr(frame1);

% invert sources
frame1 = imcomplement(frame1);
frame2 = imcomplement(frame2);

% reduce each image to grayscale (same thing imfuse() does)
frame1 = im2gray(frame1);
frame2 = im2gray(frame2);

% assemble two secondary-color images
blank = zeros(size(frame1));
frame1 = cat(3,blank,frame1,frame1); % cyan
frame2 = cat(3,frame2,frame2,blank); % yellow

% combine them by addition, invert
outpict = imcomplement(frame1 + frame2);

imshow(outpict)

That doesn't look so bad. In fact, in some cases, this might be preferable. Let's see what happens when we try this with our high-contrast black-on-white images.

frame1 = imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/83841/frame0017.png');
frame2 = imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/83840/frame0031.png');

% invert sources
frame1 = imcomplement(frame1);
frame2 = imcomplement(frame2);

% reduce each image to grayscale (same thing imfuse() does)
frame1 = im2gray(frame1);
frame2 = im2gray(frame2);

% assemble two secondary-color images
blank = zeros(size(frame1));
frame1 = cat(3,blank,frame1,frame1); % cyan
frame2 = cat(3,frame2,frame2,blank); % yellow

% combine them by addition, invert
outpict = imcomplement(frame1 + frame2);

imshow(outpict)

We lose color mixing in the overlap regions, since the combination of two secondary colors truncates to white.