Draw multiple circles in one image

Hello, everyone,

I need your help. I wanted to draw several circles in one picture and edit them later. Attached is a screen shot. thank you for your help

Latifa

Answer 1

[KSSV]

R = 2:2:10 ;
th = linspace(0,2*pi) ;
figure
hold on
for i = 1:length(R)
    x = R(i)*cos(th) ; 
    y  = R(i)*sin(th) ; 
    plot(x,y)
end
axis equal

[Latifa Bouguessaa]

thanks sir for your help

how can I cut off the individual circles from the image for further processing? is there a function for this?

[Latifa Bouguessaa]

i tried again but without success

here is my code:

image = imread('cameraman.tif');
figure(1)
imshow(image,'DisplayRange',[]);
xc=128;
yc=128;
theta=linspace(0,2*pi);
c0=1;
r=[10,20,30,40,50];
for i = 1:length(r)
    x = r(i)*cosd(theta) + xc;
    y = r(i)* sind(theta) + yc;
    pos = [x, y];
    viscircles([x(i),y(i)],1,'LineStyle','-','LineWidth',1);
    %viscircles('Position', pos, 'EdgeColor', 'g', 'LineWidth', 1)
    axis square;
    grid on;
    subimage(:,:,co) = imcrop(image, pos);
    co=co+1;
end

Error using images.internal.crop.parseInputsOverTwo>validateRectangle
Input number 2, RECT, is expected to contain 4 elements.

Error in images.internal.crop.parseInputsOverTwo (line 54)
validateRectangle(spatial_rect,2);

Error in imcrop (line 104)
images.internal.crop.parseInputsOverTwo(varargin{:});

figure(2)
imshow(subimage,'DisplayRange',[]);

[Walter Roberson]

img = imread('cameraman.tif');
figure(1)
imshow(img, 'DisplayRange', []);

[r, c, p] = size(img);
xc = 128;
yc = 128;

r=[10,20,30,40,50];

for i = 1:length(r)
    ROI = images.roi.Circle('Center', [xc, yc], 'Radius', r(i));
    mask = cast(repmat(createMask(ROI, img), [1, 1, p]), class(img));
    masked_img = img .* mask;
    subimage{i} = imcrop(masked_img, [xc-r(i), yc-r(i), 2*r(i)+1, 2*r(i)+1]);
end

for i = 1 : length(r)
    figure
    imshow(subimage{i}); title(string(r(i)));
end

[Latifa Bouguessaa]

Hello Walter Roberson, thanks for your help. this is exactly what i need

[Latifa Bouguessaa]

Hello everyone.

thank you all for your help.

I still have a few questions though.

how can I call up and edit the individual ROIs from subimage{i}?

next task is to calculate the FFT of each ROI. How can I only edit the values inside the circle.

I thank you in advance

[Image Analyst]

"how can I call up and edit the individual ROIs from subimage{i}?" <= you already have subimage{i}, so it's already "called up". To edit it, you assign values to certain rows and columns of it.

"next task is to calculate the FFT of each ROI." <= call ftImage = fft2(subimage{i}); The fft will apply to the entire rectangular image including the black masked off portions.

"How can I only edit the values inside the circle." <= I already told you how to edit the image. Just give row and column values inside the circle and reassign those intensity values.

[Latifa Bouguessaa]

Thank you for your help Image Analyst

I tried to solve the task like this, but it doesn't work, I don't know what the problem is. Here is my code:

for i=1:length(r)

mm = mean(mean(subimage{i}(subimage{i}~=0)));

subimage{i}=(subimage{i}(subimage{i}~=0))-mm;

spe{i}= (abs(fftn(subimage{i}))).^2;

%pixel spacing

Deltax=Spasi(1);

Deltay=Spasi(2);

f=(Deltax*Deltay)/size(subimage{i},1).^2;

w4{i}=mean(spe{1,i});

nps{i}=f*w4{i};

nps{i}=nps{1,i}/sum(nps{i});

spaki=Spasi(1,1);

[q g]=size(nps{i});

%Frequency

frequency=(1/((r(i)+1)*2*spaki));

sumbu=0:frequency:(((g-1)*frequency));

hold on

figure(5)

subplot(3,2,i)

hold on;

plot(sumbu, nps{i}, 'o--')

xlabel('Spatial Frquency ?mm?^-1')

ylabel('NPS)

set(gcf, 'color', 'w')

end

[Image Analyst]

I have no idea what you want to do. All professional programmers put comments into their code. Where are yours? Explain every section or line of your code up until the plotting part.

[Walter Roberson]

You cannot reliably recreate the roi given just the subimage and comparing it to 0, as interior pixels could be 0.

You could, it is true, take the subimage and fit a circle to it to recreate the roi.

But if you are going to need the roi later, just record the mask variables as well, it saves a lot of trouble.