Plot a circle of desired intensity.

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Jose Aroca
Jose Aroca 2020-6-11
评论： Image Analyst 2020-6-12
I have the following code to draw a white square on a black background. The intensity of the square can be varied from 0 to 256 from black to white.
backg = uint8(zeros(500,500,3));%produce 500x500 px background
for x = 200:1:300; %define x limits of square
for y = 200:1:300; %define y limits of square
backg(x,y,:) = 256; %choose intensity
end;
end;
image(backg);
I would like to use the same code to plot a circle, but I get errors related to array indices.
Many thanks.

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采纳的回答

Image Analyst
Image Analyst 2020-6-12
Code is in the FAQ: https://matlab.fandom.com/wiki/FAQ#How_do_I_create_a_circle.3F
Adapt as needed (center location, radius, intensity, etc.).
  2 个评论
Jose Aroca
Jose Aroca 2020-6-12
Yeah, I saw that before. However, I want a circle in which the intensity can be varied. I developed this code in which the intensity can be varied according to the radius.
imagelength=100;
middle=(imagelength+1)/2;
radius=20;
dimmerRadius=15;
brightness=256;
dimmerBrightness=150;
image=ones(imagelength);
for i=1:imagelength
x=-imagelength+middle+i; %change y coordinate by adding term
for j=1:imagelength
y=-imagelength+middle+j; %change x coordinate by adding term
if(x^2+y^2<=radius^2) %equation of desired shape
image(i,j)=brightness;
end
if(x^2+y^2<=dimmerRadius^2)
image(i,j)=dimmerBrightness;
end
end
end
imagesc(image)
axis square
axis off
colormap gray
caxis([1 256])
However, I want the intensity to vary as a Gaussian, ie. to be maximum at the centre and tail off as r is increased. Any ideas?

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