Which algorithm for counting the occurrences of a certain pattern (spots) in an image?

The Problem :

Finding the number of occurrences of a certain pattern (or shape) in an image. In my example, the problem is about finding the number of spots (in variety of sizes) in an image. See figure 1 below:

What I'm looking for here is an orientation. What class of algorithms can lead to a solution for this type of problems?

The best way to get an orientation is to read a textbook on computer vision or image processing. There are lots of techniques known, and that's often the best way to get an introduction to a broad topic like this.

Anyway, for some specific techniques, I would recommend that you learn about the following candidate approaches:

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Learn about morphological operators, and experiment with a few combinations of them.

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Learn about the watershed transform, which might solve your problem immediately. More generally, learn about image segmentation techniques, of which there are many.

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You might want to consider applying thresholding to the image as a pre-processing step.

Your task looks pretty easy, so I imagine you should be able to find a very effective combination of techniques if you learn about them and try them out on sample images.

StackExchange Computer Science Q#55511, answer score: 3