Sphere-based color slicing of image

Sphere based color slicing

Answer 1

[Image Analyst]

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);

Answer 2

[Image Analyst]

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