trying to make a donut mask to span over images, suggestions?

[x,y] = meshgrid(1:width, 1:height);

centerX = (width + 1) / 2;

centerY = (height + 1) / 2;

dist = sqrt((x - centerX).^2 + (y - centerY).^2);

innerRadius = 50;

outerRadius = 100;

masksign = false(height, width);

masksign(dist >= innerRadius & dist <= outerRadius) = true;

masksign = grayImage >= lowThreshold & grayImage <= highThreshold;

imshow(masksign);

Answer 1

[Kevin Holly]

RGBImage = imread("peppers.png");
imshow(RGBImage)

size(RGBImage)

ans = 1×3

384 512 3

width = 300;
height = 300;
[x,y] = meshgrid(1:width, 1:height);
    centerX = (width + 1) / 2;
    centerY = (height + 1) / 2;
    dist = sqrt((x - centerX).^2 + (y - centerY).^2);
    innerRadius = 50;
    outerRadius = 100;
    masksign = false(height, width);
    masksign(dist >= innerRadius & dist <= outerRadius) = true;
%     masksign = grayImage >= lowThreshold & grayImage <= highThreshold;
    figure
    imshow(masksign);

    size(masksign)

ans = 1×2

300 300

    figure
    imshow(uint8(masksign).*RGBImage(1:300,1:300,:))

[Neo]

Thank you Dr.@Kevin Holly, to follow up I want to make it a half donut mask

width = 300;

height = 300;

% Create a meshgrid

[x,y] = meshgrid(1:width, 1:height);

% Set the center coordinates of the donut

centerX = (width + 1) / 2;

centerY = (height + 1) / 2;

% Calculate the distance of each point from the center

dist = sqrt((x - centerX).^2 + (y - centerY).^2);

% Set the radii of the inner and outer circles

innerRadius = 50;

outerRadius = 100;

% Create a logical array for the mask

masksign = false(height, width);

% Set the region between the radii to true

masksign(dist >= innerRadius & dist <= outerRadius) = true;

% Set the region above the center to false

masksign(1:centerY,:) = false;

% Display the mask

figure

imshow(masksign);

and then make 9 evenly distributed half donut masks across the image would this be the next step? But i can only get it half on the x axis but i want to half it over the y axis.

% Define the number of half donut masks to create

numMasks = 9;

% Define the size of the image

width = 300;

height = 300;

% Calculate the width of each mask

maskWidth = floor(width / numMasks);

% Create a meshgrid

[x,y] = meshgrid(1:width, 1:height);

% Loop through each mask and create a half donut mask

for i = 1:numMasks

% Calculate the center coordinates of the mask

centerX = (maskWidth * (i - 0.5));

centerY = (height + 1) / 2;

% Calculate the distance of each point from the center

dist = sqrt((x - centerX).^2 + (y - centerY).^2);

% Set the radii of the inner and outer circles

innerRadius = 50;

outerRadius = 100;

% Create a logical array for the mask

masksign = false(height, maskWidth);

% Set the region between the radii to true

masksign(dist >= innerRadius & dist <= outerRadius) = true;

% Set the region above the center to false

masksign(1:centerY,:) = false;

% Display the mask

subplot(1,numMasks,i);

imshow(masksign);

end

Ultimately, I want to be able to use the mask to count the number of shapes at that particular location and plot the number of shapes counted vs their location (9 different locations same number as the mask).

[Kevin Holly]

I am not sure what exactly you are trying to accomplish. Below, I rotated the images you create to show a half donut halved vertically.

width = 300;
height = 300;
% Create a meshgrid
[x,y] = meshgrid(1:width, 1:height);
% Set the center coordinates of the donut
centerX = (width + 1) / 2;
centerY = (height + 1) / 2;
% Calculate the distance of each point from the center
dist = sqrt((x - centerX).^2 + (y - centerY).^2);
% Set the radii of the inner and outer circles
innerRadius = 50;
outerRadius = 100;
% Create a logical array for the mask
masksign = false(height, width);
% Set the region between the radii to true
masksign(dist >= innerRadius & dist <= outerRadius) = true;
% Set the region above the center to false
masksign(1:round(centerY),:) = false;
% Display the mask
figure
imshow(masksign);

stacked_vertically = [];

% Define the number of half donut masks to create
numMasks = 9;
% Define the size of the image
width = 300;
height = 300;
% Calculate the width of each mask
maskWidth = floor(width / numMasks);
% Create a meshgrid
[x,y] = meshgrid(1:width, 1:height);
% Loop through each mask and create a half donut mask
for i = 1:numMasks
    
    % Calculate the center coordinates of the mask
    centerX = (maskWidth * (i - 0.5));
    centerY = (height + 1) / 2;
    
    % Calculate the distance of each point from the center
    dist = sqrt((x - centerX).^2 + (y - centerY).^2);
    
    % Set the radii of the inner and outer circles
    innerRadius = 50;
    outerRadius = 100;
    
    % Create a logical array for the mask
%     masksign = false(height, maskWidth);
    
    % Set the region between the radii to true

    masksign = dist >= innerRadius & dist <= outerRadius;
    
    % Set the region above the center to false
    masksign(1:round(centerY),:) = false;
    
    % Display the mask
    subplot(2,numMasks,i);
    imshow(masksign);

    % Display the mask
    subplot(2,numMasks,i+numMasks);
    imshow(imrotate(masksign,90)); 

    stacked_vertically = [stacked_vertically ; imrotate(masksign,90)];
end

figure
imshow(stacked_vertically)

[Neo]

Hi Dr. @Kevin Holly Thank you for this it really helped.

I am trying to get my attached script to work.

My code is attempting to count the number of dots (using a left half donut shaped mask) over 12 (or 9 the number is arbitrary) consecutive locations evenly distributed across the image and plot the count of the content as a function of the location.

My issues are the integer values are either not logical, or not positive and my code doesn't like that. Everytime I think I fix it, some other related error pops up. I thought the issue was the mask, then the maxDistance but now i am unsure. What would you suggest? Thank you.