how to crop an image equally

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Ruksana siddique 2019-3-5

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https://ww2.mathworks.cn/matlabcentral/answers/448361-how-to-crop-an-image-equally

回答： Ruksana siddique 2019-3-8

i want to divide this picture equally from the centre of the optic disc on a angle of 30 degree. but i dont no how to dvide it. I need a algorithm for this. i am sharing an demo image.. i have to crop thi im592 image in demo type image

i want crop this image in patches so that i can extraxct its feature

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采纳的回答

KSSV 2019-3-5

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/448361-how-to-crop-an-image-equally#answer_363909

在 MATLAB Online 中打开

I = imread('Im592.jpg') ;
[ny,nx,nz] = size(I) ;
[X,Y] = meshgrid(1:nx,1:ny) ;
C = round([nx/2 ny/2]) ;  % center 
R = abs(min(C)-min(nx,ny)) ;
% circle 
th = linspace(0,pi/2) ;
x = C(1)+R*cos(th) ; 
y = C(2)+R*sin(th) ;
figure
imshow(I)
hold on
plot(x,y,'r')
% Get inside part / crop
xp = [0 x 0] ; yp = [0 y 0] ;
idx = inpolygon(X(:),Y(:),xp,yp) ;
%
for i = 1:3
    T = I(:,:,i) ;
    T(~idx) = 255 ;
    I(:,:,i) = T ;
end
    
figure
imshow(I)