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

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

Draw multiple circles in one image

Latifa Bouguessaa 2022-7-27

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 2022-7-27

编辑：Walter Roberson 2022-7-30

在 MATLAB Online 中打开

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 2022-7-30

在 MATLAB Online 中打开

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 2022-7-31

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

Latifa Bouguessaa 2022-8-12

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 2022-8-12

"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 2022-8-12

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 2022-8-12

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 2022-8-12

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.

Draw multiple circles in one image

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