How can we extract objects from a greyscale image?

So, i got a grayscale image of a box, which contains some objects.. I need to identify if/ not the box is empty or not....

I tried using the otsu thresholding, but doesn't work properly. is it possible to convert all the other parts to black except the image of interest?

[Walter Roberson]

How do you know which part is of interest before you have done the thresholding ?

[Nihar Rupareliya]

This is the image of bucket which is full. the spatula, etc are the part of interest.

[Walter Roberson]

I would recommend background subtraction, if you can get a picture of the empty bucket, especially if everything is taken from a fixed viewpoint (if the viewpoint is not fixed then you might need to do image registration before doing the subtraction.)

Answer 1

[darova]

What about bwareaopen()

I = imread('example_filled2.jpg');
I1 = I < 40;
I2 = bwareaopen(I1,3e3);
imshow(I2)

What i've got