How do I remove blobs connected to border?

I want to remove objects connected to the border of AOI (Area of interest). I'm not sure what I should do to solve this problem. I'm aware of the imclearborder() function, but this only removes objects along the border of the image itself. I want to remove the red rice shown below:

Any tips or advice would greately appreciated. Thank you!

Answer 1

[DGM]

This is one way. Use the ROI mask to connect the truncated blobs to the image border. Then you can use imclearborder().

% an image
A = imread('rice.png');

% binarize the rice somehow
mkrice = bwareaopen(A>130,100);

% create an ROI mask somehow
imshow(A);
ROI = images.roi.Polygon(gca);
ROI.Position = [88 28;41 84;36 159;140 211;228 124;220 28;141 62];

mkroi = createMask(ROI);

% show what we have
imshow([mkrice mkroi])

% combine the two and discard 
mkout = imclearborder(mkrice | ~mkroi);

imshow(mkout)

[Image Analyst]

And the count is???

[DGM]

What count? Nobody said anything about counting. That might be part of the assignment, but it's up to the person asking a question about homework to decide which parts of the task they need help with.

[Image Analyst]

Don't know what I was thinking. Maybe that he wanted to find the red rice - I don't remember. Sorry, never mind.

[DGM]

It's okay. Some things get repeated so often I'm already starting to get flashbacks of similar cases myself.

Answer 2

[Image Analyst]

You've probably figured it out by now but I'd use bwperim and imreconstruct.

Let me know if you can't figure it out and I'll give you the solution tomorrow.