Draw Circle on picture and then save the drawn circle on the picture

Hi there,

I am trying to open a picture in matlab, then draw a circle on it using p = drawcircle('LineWidth',3,'Color','black');

up until here everything works well. I do not manage to export the drawn circle together with the picture as a new file.

Any help is much appreciated!

Here 'all' the code for now:

image=imread('IMG_6309.jpeg');

imshow(img)

p = drawcircle('LineWidth',3,'Color','black');

Answer 1

[KSSV]

Image = imread('peppers.png');

imshow(Image)
% plot circle 
hold on
th = 0:pi/50:2*pi;
R = 50 ; 
C = round([size(Image,2)/2 size(Image,1)/2]) ; 
xunit = R * cos(th) + C(1);
yunit = R * sin(th) + C(2);
plot(xunit, yunit, 'r');
% plot the circle center
scatter(C(1), C(2), 20, 'r+');
hold off
F = getframe ;
% save the image:
imwrite(F.cdata,'test.png')

[Elmar Kert]

Hi KSSV, thanks for your quick response, much appreciated. This works, yes, but what I would like to do is draw the circle myself around certain objects in the picture. Using the code provided by you does not seem to allow this.

[KSSV]

I have shown you a demo code..... you use your function drawcircle, to get the job done.

[Elmar Kert]

ah go it, it's working now thank you! Do you also happen to know how to count the numbers of pixels inside the circle? :)

[KSSV]

clc; clear all ;
Image = imread('peppers.png');

imshow(Image)
% plot circle 
hold on
th = 0:pi/50:2*pi;
R = 50 ; 
C = round([size(Image,2)/2 size(Image,1)/2]) ; 
xunit = R * cos(th) + C(1);
yunit = R * sin(th) + C(2);
plot(xunit, yunit, 'r');
% count pixels inside the circle 
x = 1:size(Image,2) ; 
y = 1:size(Image,1) ; 

[X,Y] = meshgrid(x,y) ; 

idx = inpolygon(X,Y,xunit,yunit) ; 

nnz(idx)