How do I change from Square to CIrcle?

This fresnel diffraction simulation for a square aperture. I need to change it to work with a circle aperture. I need to help to change this step:

u0(257-w*20:256+w*20,257-w*20:256+w*20)=1; % setup aperture

This for a square and how i convert it to a circle?

Thank you.

The code is:

2d propagation from square apertures

ii=sqrt(-1) lambda= .365; % wavelenght [µm] z=1; % distance [µm] w=1; % width of slit is 2*w [µm]

x=-12.75:0.05:12.8; % setup spatial axis [µm] freqx=-10:20/512:10-1/512; % setup frequency axis [1/µm] freqy=freqx;

u0=zeros(512); % field at z=0 a0=zeros(512); % angular spectrum at z=0 H=zeros(512); % transfer function az=zeros(512); % angular spectrum at z=z uz=zeros(512); % field at z=z

for nx=1:512 % setup transfer function for ny=1:512 H(nx,ny)=exp(ii*2*pi*(z/lambda)*... sqrt(1-(lambda*freqx(nx))^2-(lambda*freqy(ny))^2)); end end

u0(257-w*20:256+w*20,257-w*20:256+w*20)=1; % setup aperture a0=(fftshift(fft2(u0))); % fourier transform az=a0.*H; % multiply with transfer function uz=ifft2(fftshift(az)); % inverse fourier transform p=uz.*conj(uz);

figure(1) plot(x, p(:,256)); % plot of cross-section of intensity at z xlabel('x'); ylabel('I');

figure(2) imagesc(x, x, p); %diffraction pattern at z xlabel('x'); ylabel('y'); colormap(gray); colorbar;

Answer 1

[Image Analyst]

See code examples for creating a circle in the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F. You can adapt them as needed.

[Dina Abd El-twab]

Can I convert this rectangle to be a circle and show the circle on the image ?

Image Analyst

[Image Analyst]

Start a new question on this if you still have questions after looking at the documentation for viscircles(). And say what you know, like did you know the (x, y, width, height) of the rectangle.

viscircles([x+width/2, y+height/2], mean([width, height]));

[Image Analyst]

Dina's "Answer" moved here since it's a reply to me, not an Answer to the original question:

Image Analyst

How can I calculate the width and height of the rectangle in this image automatically?

[Dina Abd El-twab]

I asked a new question and i tagged you.

This is the link of the question , please reply

https://www.mathworks.com/matlabcentral/answers/510847-measure-the-width-and-height-of-the-rectangle-in-this-image-automatically

Image Analyst

[Image Analyst]

Well how did you draw the rectangle on there in the first place? If you didn't do it, then who did? And could you get the coordinates from them? If not, you can get it from the image by taking a mask of the rectangle.

[Dina Abd El-twab]

I didn't understand ,how can i make a mask to the rectangle ? could you clarify please

Image Analyst

[Image Analyst]

Where is your new question (so we don't keep sending Maitham emails)? Your link above no longer works.

yellowMask = rgbImage(:,:,1) == 255 & rgbImage(:,:,2) == 255 & rgbImage(:,:,3) == 0;
yellowMask = imfill(yellowMask, 'holes');
yellowMask = bwareafilt(yellowMask, 1);
props = regionprops(yellowMask, 'Centroid', 'EquivDiameter');
viscircles(props.Centroid, props.EquivDiameter/2);

[Dina Abd El-twab]

this code didn't give me what i want ,could you please open this link , Iam gonna attach what happened in this link now to contact there

Image Analyst

https://www.mathworks.com/matlabcentral/answers/510856-calculate-the-width-and-height-of-the-rectangle-in-this-image-automatically