MATLAB Answers

Sphere-based color slicing of image

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Accepted Answer

Image Analyst
Image Analyst on 26 May 2020
Sucharita: Here, I've done 95% of it for you. If I do much more, then you'd just be turning in my answer as your own and I don't think your course rules allow that. You just need to replace the line that says "% code" with your own code and then display the output image after the loop is done.
% Demo to find color distances in RGB color space. By Image Analyst, May 26, 2020.
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);
a1 = [134, 51, 143]
a2 = [131, 132, 4]
R0 = 30
%-----------------------------------------------------------------------------------------------------------------------------------
% Read in image.
folder = pwd;
baseFileName = 'image.jpeg';
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 test image full size.
subplot(2, 2, 1);
imshow(rgbImage, []);
axis('on', 'image');
caption = sprintf('Reference Image : "%s"', baseFileName);
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';
[rows, columns, numberOfColorChannels] = size(rgbImage);
outputImage = zeros(rows, columns, numberOfColorChannels, class(rgbImage));
distanceImage = zeros(rows, columns);
for col = 1 : columns
for row = 1 : rows
thisR = double(rgbImage(row, col, 1));
thisG = double(rgbImage(row, col, 2));
thisB = double(rgbImage(row, col, 3));
distanceImage(row, col) = sqrt((thisR - a1(1))^2 + (thisG - a1(2))^2 + (thisB - a1(3))^2); % or a2 for case ii
if distanceImage(row, col) < R0
% code...
end
end
end
maxDistance = max(distanceImage(:))
% Display the distance image.
subplot(2, 2, 2);
imshow(distanceImage, []);
axis('on', 'image');
caption = sprintf('Distance Image : "%s"', baseFileName);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
colorbar;
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
% Display the histogram of the distance image.
subplot(2, 2, 3);
histogram(distanceImage, 256);
grid on;
title('Histogram of Color Distances', 'FontSize', fontSize, 'Interpreter', 'None');
xlabel('Gray Level', 'FontSize', fontSize, 'Interpreter', 'None');
ylabel('Count', 'FontSize', fontSize, 'Interpreter', 'None');
fprintf('Done running %s.m ...\n', mfilename);

  1 Comment

Sucharitha Chokkappa Gari
Sucharitha Chokkappa Gari on 26 May 2020
Thank you so Much sir you really helped me a lot...... I will do the remaning.

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More Answers (1)

Image Analyst
Image Analyst on 25 May 2020
Edited: Image Analyst on 26 May 2020
Just scan the image pixel by pixel getting the RGB color. Then compute the color distance and if it's less than R0, copy that color to an output image. Here's a start:
[rows, columns, numberOfColorChannels] = size(rgbImage);
outputImage = zeros(rows, columns, numberOfColorChannels, class(rgbImage));
for col = 1 : columns
for row = 1 : rows
thisR = double(rgbImage(row, col, 1));
thisG = double(rgbImage(row, col, 2));
thisB = double(rgbImage(row, col, 3));
distance = sqrt((thisR - a1(1))^2 + .........) % or a2 for case ii
if distance < R0
% code...
end
end
end

  1 Comment

Sucharitha Chokkappa Gari
Sucharitha Chokkappa Gari on 26 May 2020
Sir, I tried to copy the color to output image but it says Index error

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