MATLAB: How to generate a circle within a digital image

digital image processingimageMATLAB

Hi all,

I am working on a function H for generating a circle of radius R centered within an M-by-N digital image. The prompt suggests that I use imshow to visualize the image H for various values of R, M, and N. My issue is with generating the M-by-N digital image. I have been unable to find relevant documentation.

I am not familiar with the digital image processing capabilities of MATLAB and I am working on some exercises in anticipation for a digital image processing course. Any help would be greatly appreciated.

Best Answer

I = imread('peppers.png') ; 
[nx,ny,nz] = size(I) ; 
C = [round(ny/2) round(nx/2)] ;  % center of circle 
R = 100 ;  % Radius of circle 
th = linspace(0,2*pi) ; 
xc = C(1)+R*cos(th) ; 
yc = C(2)+R*sin(th) ; 
imshow(I)
hold on
plot(xc,yc,'b')

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MATLAB: How to crop circular area and measure the ratio of black and white from the binarized image

Measure the ratio of black and white from the binarized image?

Here bw_image is a input binary image.

[rows colm]=size(bw_image);
white_pixels=sum(bw_image(:));
black_pixels=~bw_image;
black_pixels=sum(black_pixels(:));
result=bwareafilt(~bw_image,1,'Largest');
outer_black=sum(result(:));
% Area with respect to circle only
black_pixels_area=(black_pixels-outer_black)/((rows*colm)-outer_black);
fprintf('The Percentage of black pixels covered area is %.2f ',black_pixels_area);
fprintf('\n The ratio black/white is %.2f',black_pixels/white_pixels);

MATLAB: Find points of intersection circle with line

clc; clear all ;
C = [1.5 1.5] ;   % center of cricle 
r = 1.5 ;         % radius of circle 
% 
x = 0:1:3 ; 
y = 0:1:3 ; 
[X,Y] = meshgrid(x,y) ; 
%
th = linspace(0,2*pi) ; 
xc = C(1)+r*cos(th) ; 
yc = C(2)+r*sin(th) ; 
L1 = [xc;yc] ;
% GEt intersecdtion points 
% along X 
[m,n] = size(X) ; 
for i = 1:m
  L2 = [X(i,:) ; Y(i,:)] ; 
  P{i} = InterX(L1,L2)
end
for i = 1:n
  L2 = [X(:,i) Y(:,i)]' ;
  Q{i} = InterX(L1,L2) ;
end
P = cell2mat([P Q]) ;
plot(xc,yc,'b') ;
hold on
plot(X,Y,'r')
plot(X',Y','r')
plot(P(1,:),P(2,:),'*k')

InterX can be downloaded from here: https://in.mathworks.com/matlabcentral/fileexchange/22441-curve-intersections?focused=5165138&tab=function

Best Answer

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MATLAB: How to crop circular area and measure the ratio of black and white from the binarized image

MATLAB: Find points of intersection circle with line

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