How to fill the unclosed shape?

I am now trying to create a mask to use in a machine learning annotation file.

In doing so, I would like to binarize the droplet image with a threshold value and then fill the inside of the droplet with imfill.

However, sometimes the boundary becomes an open curve due to some thinness in the boundary area.

In this case, what can I do to fill this area automatically?

Here is the code.

This is the first time to ask a question on matlab and I am not a fluent in English, so I apologize if there is any rudeness.

I_pp=double(rgb2gray(imread("img0.jpg")));
%I_bg=double(rgb2gray(imread("bg.jpg")));
diff=I_pp; %-I_bg;
min(min(diff))
result=((diff-min(min(diff)))/(max(max(diff))-min(min(diff))));
imshow(result)
level=graythresh(result);
BW=imbinarize(result,level);
BW(1:7, :)=1;
BW(end-7:end,:)=1;
BW= 1-BW;
BW2 = bwmorph(BW, 'bridge');
BW2=imclose(BW2,strel('disk',2));
imshow(BW2)
%%
I2 = imfill(BW2,'holes');
imshow(I2)

Answer 1

[Image Analyst]

You can try imclose, but that's not your biggest problem. Your biggest problem is the non-uniformity of your illumination. It's most likely due to lens shading. You need to divide that out. First take a "blank" shot of nothing -- just the light background itself. Then divide your images with stuff in them by the background image. I attach a demo.

[Kei Mukoyama]

Thank you so much!!

I'll test it.

[Kei Mukoyama]

By the way, when I use imclose, droplets from different locations merge, is there any way to prevent this?

Is there any way to prevent this? Is the only way to prevent this is to specify the position of each droplet individually?

[Image Analyst]

Instead of imclose, you can use bwmorph with the 'thicken' option. This won't join blobs. Then follow that with an imerode with the same structuring element.