Matlab在图片上画个半圆和矩形

1. 
   
2. clc; clear all; close all;
   
3. I = imread('rice.png');
   
4. [h, w] = size(I);
   
5. r = min(h, w)/10;
   
6. figure;
   
7. imshow(I); hold on;
   
8. for i = 1 : 3
   
9.     [x0, y0] = ginput(1);
   
10.     t = linspace(pi, 2*pi);
    
11.     x = x0 + r*cos(t);
    
12.     y = y0 + r*sin(t);
    
13.     plot(x, y, 'r-', 'LineWidth', 2);
    
14.     rectangle('Position',[x0, y0, r, r], ...
    
15.         'LineWidth', 2, 'EdgeColor', 'r');
    
16. end
    

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