How to separate the foreground from the background in an image?

I need to seperate foreground(medicine and coin) from background I tried to crop image(medicine and coin) and use threshold , imclose,imopen

This is my result

but it dose not perfect.

In my intention I need use same code with all pictures (I drag picture for information)

Do you have any ideal ? Thank you.

Answer 1

[Image Analyst]

See my interactive thresholding app in my File Exchange:

Image Analyst's File Exchange

Then you can interactively adjust the threshold. If it's still not perfect, and you need perfect, you will have to fix your image capture situation. For one thing you could use a different background color. Not white but some contrasting color like green. Then you can do color segmentation with the Color Threshold App on the Apps tab of the took ribbon.

Secondly, you need to have better lighting. Either light coming from all around the sides to eliminate shadows, or a very broad overhead illumination (like large LED panel or an umbrella type of light.

Third, if you want accurate diameters you must reduce the cone angle from your lens to the subject. This means using a longer focal length lens and backing your camera away so the light rays are more parallel. Of course the best way is to use a concentric lens, rather than a regular lens. This has parallel rays entering the camera so you will never see the edges of the objects, only the tops. The downside is they're very expensive, and you'd need a lens diameter that is at least as large as your field of view.