Circular ROI is not being drawn from input - matlab

Question

For some reason, the following code only displays the masked image with roi at 10,10 with height and width 100,100. These are the initial values. It seems the image does not update even after the getPosition function. Could anyone explain this issue?
`I = imread('/Users/imageuser/Documents/PT300.tif');
h = imshow(I);
% define circular roi by square bounding box
x = 10;
y = 10;
d1 = 100;
d2 = 100;
e = imellipse(gca, [x y d1 d2]);
% roi can be interactively moved/adjusted
% do not close figure window before createMask is called
%%% these lines are only needed if you move or resize the roi
pos = getPosition(e);
x = pos(1);
y = pos(2);
d1 = pos(3);
d2 = pos(4);
%%%
BW = createMask(e,h);
pause;
imshow(BW);`

Answer 1

You need to put those lines (note I inverted their order):
pause;
BW = createMask(e,h);
before calling getPosition, otherwise the new position is not updated.
Whole code:
clear
clc
close all
I = imread('coins.png');
h = imshow(I);
% define circular roi by square bounding box
x = 10;
y = 10;
d1 = 100;
d2 = 100;
e = imellipse(gca, [x y d1 d2]);
pause;
BW = createMask(e,h);
% roi can be interactively moved/adjusted
% do not close figure window before createMask is called
%%% these lines are only needed if you move or resize the roi
pos = getPosition(e)
x = pos(1);
y = pos(2);
d1 = pos(3);
d2 = pos(4);
%%%
figure
imshow(BW);
sample output after dragging the ROI:
Yay!
Note: As mentioned by juicestain, instead of using pause to halt execution of the program while the user is done creating the GUI, you can use wait to wait until the user double-clicks on the ROI object instead of having to press a key as with the pause command.
Therefore, you could replace the call to pause with a call to wait(e).