Personalized RGB Masked Image

Hi everyone! I'm very new in MatLab Programming.

I have a RGB image and I want that certains color pixels are white, certain pixels are black and the others grey. I used the Threshold Apps (with binary mask), but I have only black or white pixels.

Answer 1

[Image Analyst]

I'm not sure what you are asking. So what does your original image look like? What do you mean that you want white, black, and gray pixels?

If you use the Color Thresholder app (on the Apps tab of the Tool Ribbon) you can find thresholds to segment out a certain color, like red for example. This will create a mask where it's true/1/white where there are red pixels and false/0/black where the pixels are not red.

Attach your image and explain better if you need more help.

TUTORIAL: How to ask a question (on Answers) and get a fast answer

[Allinone]

This is my Image. I have to extract a pair of colors (e.g. red and green), but in this case all red objects have to be white, all green objects have to be black and the rest grey. I hope it is more clear now.

[Image Analyst]

So you just use the Color Thresholder to find each color. Then export the functions. Rename one CreateRedMask() and rename the other CreateGreenmask(). Then call each

redMask = CreateRedMask(rgbImage);
% Make red mask 255
redMask = uint8(255 * redMask);
% Get the green mask
greenMask = CreateGreenMask(rgbImage);
% Create gray mask.  It's all gray except where it's red or green.
grayMask = true(size(redMask)) & ~redMask & ~greenMask;
% Make final image by adding red mask image to gray mask image.
% Green is zero so no need to add it in.
output = uint8(255 * redMask + 128 * grayMask);
imshow(output, [])

[Allinone]

Ok, thank you so much, but where do I have to write this code?

redMask = CreateRedMask(rgbImage);
% Make red mask 255
redMask = uint8(255 * redMask);
% Get the green mask
greenMask = CreateGreenMask(rgbImage);
% Create gray mask.  It's all gray except where it's red or green.
grayMask = true(size(redMask)) & ~redMask & ~greenMask;
% Make final image by adding red mask image to gray mask image.
% Green is zero so no need to add it in.
output = uint8(255 * redMask + 128 * grayMask);
imshow(output, [])

[Image Analyst]

Attached is a full demo:

% Demo by Image Analyst.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clearvars;
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 16;
fprintf('Beginning to run %s.m ...\n', mfilename);
%-----------------------------------------------------------------------------------------------------------------------------------
% Read in image.
folder = [];
baseFileName = 'peppers.png';
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
rgbImage = imread(fullFileName);
[rows, columns, numberOfColorChannels] = size(rgbImage)
% Display the image.
subplot(2, 3, 1);
imshow(rgbImage, []);
axis('on', 'image');
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
caption = sprintf('Original RGB Image : "%s"\n%d rows by %d columns', baseFileName, rows, columns);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
% Set up figure properties:
% Enlarge figure to full screen.
hFig1 = gcf;
hFig1.Units = 'Normalized';
hFig1.WindowState = 'maximized';
% 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.
hFig1.Name = 'Demo by Image Analyst';
%-----------------------------------------------------------------------------------------------------------------------------------
% Get the red mask
[redMask, maskedRGBImageR] = createRedMask(rgbImage);
% Display the image.
subplot(2, 3, 2);
imshow(redMask, []);
axis('on', 'image');
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
title('Red Mask', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
% Display the image.
subplot(2, 3, 3);
imshow(maskedRGBImageR, []);
axis('on', 'image');
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
title('Red Mask', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
%-----------------------------------------------------------------------------------------------------------------------------------
% Get the green mask
[greenMask, maskedRGBImageG] = createGreenMask(rgbImage);
% Display the image.
subplot(2, 3, 5);
imshow(greenMask);
axis('on', 'image');
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
title('Green Mask', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
% Display the image.
subplot(2, 3, 6);
imshow(maskedRGBImageG, []);
axis('on', 'image');
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
title('Green MaskedImage', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
%-----------------------------------------------------------------------------------------------------------------------------------
% Create gray mask.  It's all gray except where it's red or green.
grayMask = true(size(redMask)) & ~redMask & ~greenMask;
% Make final image by adding red mask image to gray mask image.
% Green is zero so no need to add it in.
output = uint8(255 * redMask + 128 * grayMask);
% Display the image.
subplot(2, 3, 4);
imshow(output);
axis('on', 'image');
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
title('Gray Image', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
msgbox('Done!');
%======================================================================================================================
function [BW,maskedRGBImage] = createRedMask(RGB)
%createMask  Threshold RGB image using auto-generated code from colorThresholder app.
%  [BW,MASKEDRGBIMAGE] = createMask(RGB) thresholds image RGB using
%  auto-generated code from the colorThresholder app. The colorspace and
%  range for each channel of the colorspace were set within the app. The
%  segmentation mask is returned in BW, and a composite of the mask and
%  original RGB images is returned in maskedRGBImage.
% Auto-generated by colorThresholder app on 25-Oct-2021
%------------------------------------------------------
% Convert RGB image to chosen color space
I = rgb2hsv(RGB);
% Define thresholds for channel 1 based on histogram settings
channel1Min = 0.934;
channel1Max = 0.043;
% Define thresholds for channel 2 based on histogram settings
channel2Min = 0.318;
channel2Max = 1.000;
% Define thresholds for channel 3 based on histogram settings
channel3Min = 0.000;
channel3Max = 1.000;
% Create mask based on chosen histogram thresholds
sliderBW = ( (I(:,:,1) >= channel1Min) | (I(:,:,1) <= channel1Max) ) & ...
    (I(:,:,2) >= channel2Min ) & (I(:,:,2) <= channel2Max) & ...
    (I(:,:,3) >= channel3Min ) & (I(:,:,3) <= channel3Max);
BW = sliderBW;
% Initialize output masked image based on input image.
maskedRGBImage = RGB;
% Set background pixels where BW is false to zero.
maskedRGBImage(repmat(~BW,[1 1 3])) = 0;
end
%======================================================================================================================
function [BW,maskedRGBImage] = createGreenMask(RGB)
%createMask  Threshold RGB image using auto-generated code from colorThresholder app.
%  [BW,MASKEDRGBIMAGE] = createMask(RGB) thresholds image RGB using
%  auto-generated code from the colorThresholder app. The colorspace and
%  range for each channel of the colorspace were set within the app. The
%  segmentation mask is returned in BW, and a composite of the mask and
%  original RGB images is returned in maskedRGBImage.
% Auto-generated by colorThresholder app on 25-Oct-2021
%------------------------------------------------------
% Convert RGB image to chosen color space
I = rgb2hsv(RGB);
% Define thresholds for channel 1 based on histogram settings
channel1Min = 0.145;
channel1Max = 0.491;
% Define thresholds for channel 2 based on histogram settings
channel2Min = 0.333;
channel2Max = 1.000;
% Define thresholds for channel 3 based on histogram settings
channel3Min = 0.000;
channel3Max = 0.969;
% Create mask based on chosen histogram thresholds
sliderBW = (I(:,:,1) >= channel1Min ) & (I(:,:,1) <= channel1Max) & ...
    (I(:,:,2) >= channel2Min ) & (I(:,:,2) <= channel2Max) & ...
    (I(:,:,3) >= channel3Min ) & (I(:,:,3) <= channel3Max);
BW = sliderBW;
% Initialize output masked image based on input image.
maskedRGBImage = RGB;
% Set background pixels where BW is false to zero.
maskedRGBImage(repmat(~BW,[1 1 3])) = 0;
end

[Allinone]

Ok, thank you! Now it works. I tried with others colors, but I haven't gray level. Why do?

This is my code ( I want Yellow objects become white, green objects become black, and the rest greysh):

rgbImage = imread('....');

[rows, columns, numberOfColorChannels] = size(rgbImage);

[greenMask, maskedRGBImageG] = createGreenMask(rgbImage);

[yellowMask, maskedRGBImageY] = createYellowMask(rgbImage);

grayMask6 = true(size(greenMask)) & ~greenMask & ~yellowMask;

output = uint8(255 * yellowMask + 70 * grayMask6);

%subplot(5, 7, 13);

imshow(output);

title('G-Y');

%GREEN

function [BW,maskedRGBImage] = createGreenMask(RGB)

I = rgb2hsv(RGB);

channel1Min = 0.145;

channel1Max = 0.491;

channel2Min = 0.333;

channel2Max = 1.000;

channel3Min = 0.000;

channel3Max = 0.969;

sliderBW = ((I(:,:,1) >= channel1Min) & (I(:,:,1) <= channel1Max)) & ...

(I(:,:,2) >= channel2Min) & (I(:,:,2) <= channel2Max) & ...

(I(:,:,3) >= channel3Min) & (I(:,:,3) <= channel3Max);

BW = sliderBW;

maskedRGBImage = RGB;

maskedRGBImage(repmat(~BW,[1 1 3])) = 0;

end

function [BW,maskedRGBImage] = createYellowMask(RGB)

I = rgb2hsv(RGB);

channel1Min = 0.177;

channel1Max = 0.108;

channel2Min = 0.000;

channel2Max = 1.000;

channel3Min = 0.000;

channel3Max = 1.000;

sliderBW = ((I(:,:,1) >= channel1Min) & (I(:,:,1) <= channel1Max)) & ...

(I(:,:,2) >= channel2Min ) & (I(:,:,2) <= channel2Max) & ...

(I(:,:,3) >= channel3Min ) & (I(:,:,3) <= channel3Max);

BW = sliderBW;

maskedRGBImage = RGB;

maskedRGBImage(repmat(~BW,[1 1 3])) = 0;

imshow(maskedRGBImage);

end

[Image Analyst]

Not sure why you didn't follow my example. Anyway, did you export new functions for the new colors? And use them?

[Allinone]

Yes, I followed your example. I just deleted the parts of the code that didn't interest me and export the functions. Your code is perfect for primary colors, but what do I do with secondary and tertiary colors?

[Allinone]

This is your example, that I modiified and it works perfectly:

rgbImage = imread('...');

[rows, columns, numberOfColorChannels] = size(rgbImage);

[greenMask, maskedRGBImageG] = createGreenMask(rgbImage);

[redMask, maskedRGBImageR] = createRedMask(rgbImage);

grayMask4 = true(size(greenMask)) & ~greenMask & ~redMask;

output = uint8(255 * redMask + 70 * grayMask4);

%subplot(5, 7, 11);

imshow(output);

title('G-R');

================================================================================

%GREEN

function [BW,maskedRGBImage] = createGreenMask(RGB)

I = rgb2hsv(RGB);

channel1Min = 0.145;

channel1Max = 0.491;

channel2Min = 0.333;

channel2Max = 1.000;

channel3Min = 0.000;

channel3Max = 0.969;

sliderBW = ((I(:,:,1) >= channel1Min) & (I(:,:,1) <= channel1Max)) & ...

(I(:,:,2) >= channel2Min ) & (I(:,:,2) <= channel2Max) & ...

(I(:,:,3) >= channel3Min ) & (I(:,:,3) <= channel3Max);

BW = sliderBW;

maskedRGBImage = RGB;

maskedRGBImage(repmat(~BW,[1 1 3])) = 0;

================================================================================

%RED

function [BW,maskedRGBImage] = createRedMask(RGB)

I = rgb2hsv(RGB);

channel1Min = 0.934;

channel1Max = 0.043;

channel2Min = 0.318;

channel2Max = 1.000;

channel3Min = 0.000;

channel3Max = 1.000;

sliderBW = (I(:,:,1) >= channel1Min ) | (I(:,:,1) <= channel1Max) & ...

(I(:,:,2) >= channel2Min ) & (I(:,:,2) <= channel2Max) & ...

(I(:,:,3) >= channel3Min ) & (I(:,:,3) <= channel3Max);

BW = sliderBW;

maskedRGBImage = RGB;

maskedRGBImage(repmat(~BW,[1 1 3])) = 0;

end

[Image Analyst]

I don't understand. You just use the color thresholder for the colors you want. It doesn't matter what you call them. Make as many masks as you want then just multiply them by some number to turn them gray, and add them up like I did. What colors are you trying to do now?

[Allinone]

I understand and I did like you. I tried e.g. green and yellow, yellow and brown ecc. These not work together. In the green-yellow pairs; green objects have to be white, yellow objects have to be black and the rest greysh. In the yellow-brown pairs, yellow objects have to be black, brown ojects have to be white and the rest greysh.

[Image Analyst]

Attach the image that has all these colors that you're working with.

[Allinone]

I attached Green-Yellow and Yellow-Brown pairs. Do I have attach the code also?

[Image Analyst]

Those images do not have any green, yellow, or brown in them. Again, "Attach the image that has all these colors that you're working with." How can we fix your code if you won't give us the input image?

[Allinone]

It's the same image I attached before. I attached it again.

Answer 2

[Image Analyst]

Doing the same thing for yellow and brown is easy and straightforward.

[Allinone]

How could I show all images with pair colors in a main script (I have to show only gray Levels)?

[Image Analyst]

Copy that code multiple times with appropriate changes, or put in in a loop.

[Allinone]

I have created a function for each pair of colors. I would like to call these functions in the main script and see all the outputs, but I don't know how do i do. Sorry..I'm very new in MatLab..

Answer 3

[Image Analyst]

Doing the same thing for yellow and green is easy and straightforward.

See my other answers for different color pairs.

[Allinone]

Ok, thank you so much! I wrote the same code, but with different values, so I didn't have the gray levels..

Answer 4

[Image Analyst]

See my discriminant analysis color segmentation demo.

Also check out my delta E demo, attached.

I've posted several new answers this session so be sure to see them all.

[Allinone]

Your delta E works with all colors?

Could I detect pairs colors with your delta E, or threshold is better?

[Image Analyst]

The delta E demo identifies all pixels that are within a certain color distance of the average color that you outlined. It finds the delta E of all pixels in the image to the average color, and then thresholds it at the delta E you specify to find colors (anywhere in the image) that are close to what you drew. For example here I drew over the red pepper and it found all red pixels that are within a delta E of 21.9 from the average red in the region I drew.

For what it's worth, I'm attaching another, slightly different demo that works with two images.