How to "createMask" using "impoly" when two images are shown together in one axes by using 'AlphaData'?

Dear all,

I have two images; BW = which is a binary image, and ground_truth = which is rgb image. I tried to show them together in one axes using 'AlphaData' as shown in my code below.

I want to be able to generate a binary image (NEW_maskImage) after using the impoly in the same axes. However, I get the following error:

Ambiguous syntax. Associated axes contains more than one image. Specify image handle as input argument to resolve ambiguity.

My code as follows:

figure, imshow(BW);
hold on   % two show both images transperently
h = imshow(ground_truth, gray(256));
set(h, 'AlphaData', 0.7)

hx = impoly
wait(hx);
NEW_maskImage = hx.createMask();

Does anyone knows how to overcome this error?

Thank you very much.

Meshoo

Answer 1

[Alex Taylor]

http://www.mathworks.com/help/images/ref/imroi.html#imroi-delete

If you look at the documentation for create mask, you can optionally specify the handle of the HG image object that you want to create the mask for.

You can get this handle as an output argument when displaying your images using imshow/imagesc, etc.

[Meshooo]

Thank you very much..but how to specify the handle of the HG?