How can I draw on two ROI to create a mask on the same image?

roi = images.roi.AssistedFreehand
draw(roi)
roi2 = images.roi.AssistedFreehand
draw(roi2)
mask = createMask(roi);
mask2 = createMask(roi2);
imshow(mask);
imshow(mask2);

%imshow(BW)
J=regionfill(I,mask)
H=regionfill(I,mask2)
figure
hold on
imshow(J)
imshow(H)
hold off

I want to draw two separate regions of interest within the same image to create a mask. Then use this mask with the regionfill function. However, I am able to draw two separate ROI with this script but it does not let me combine the two together as only one region is currently being filled.

Answer 1

[Subhadeep Koley]

You can easily combine those two masks using the imadd() function. Refer the code below

close all ; clc;
I = imread('cameraman.tif');
figure; imshow(I, []);
roi = images.roi.AssistedFreehand;
draw(roi);
roi2 = images.roi.AssistedFreehand;
draw(roi2);
mask = createMask(roi);
mask2 = createMask(roi2);
% Combine 2 masks
combinedMask = imbinarize(imadd(mask, mask2));
% Apply the filter
J = regionfill(I, combinedMask);
% Display results
figure; 
subplot(2, 2, 1); imshow(mask); title('Mask 1');
subplot(2, 2, 2); imshow(mask2); title('Mask 2');
subplot(2, 2, 3); imshow(combinedMask); title('Combined Mask');
subplot(2, 2, 4); imshow(J, []); title('Region filled image');

Hope this helps!

[DGM]

I see no good reason to use imadd() and imbinarize() to calculate the union of logical-class masks.

combinedMask = mask | mask2;

If the rationale is that imadd() is safer because it will allow for the combination of binarized images of mixed class (logical and/or numeric), it's not. Tools such as imadd() have restrictions on what particular combinations of classes are allowed, and what order they're allowed in. Generally speaking imadd(), etc are not class-agnostic.

If you wanted something that is class-agnostic, you might do something like this

combinedMask = imbinarize(mask) | imbinarize(mask2);

... but in this specific example, it's unnecessary. The masks come straight from createMask(), and will always be logical-class.