Primitive Feature Detection to Detect a Black Circle within an Image

Question

I am trying to check whether this black circle is exist or not on my images.

enter image description here

My current approach is like that;

enter image description here

I just want to know is this method useful if this algorithm go for real time check ? if not what kind of methods you could suggest me ?

Here is a image with blackhole

enter image description here

Here is a image without a blackhole.

enter image description here

Could you post images after each step of your current algorithm ? Will the black hole always be centered in the image ? If so, you can crop the image to begin with, which will mean less pixels to analyze, so more time to perform analysis. — Loufylouf, Commented Mar 19, 2015 at 12:24
If the both the image and coin sizes keep the same, can you just check the pixel values within a small circle region around the center? Hough detection might be an overkill in your case. — lennon310, Commented Mar 19, 2015 at 14:03

Royi · Accepted Answer · 2023-07-15 18:46:36Z

I think you can use a much simpler method.

The steps I did are:

I think once you look at it, it will be easy to build a model.
Let's see the image without the black circle:

From ~150 to ~250 we see mostly a flat zone.

Now, let's see the image with the black circle:

Now, on the same segment we see 2 levels.

This is a great feature to classify with.

The code is available at my StackExchange Codes Signal Processing GitHub Repository (Look at the SignalProcessing\Q22183 folder).

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