cv.SimpleBlobDetector

Class for extracting blobs from an image

The class implements a simple algorithm for extracting blobs from an image:

Convert the source image to binary images by applying thresholding with several thresholds from MinThreshold (inclusive) to MaxThreshold (exclusive) with distance ThresholdStep between neighboring thresholds.
Extract connected components from every binary image by cv.findContours and calculate their centers.
Group centers from several binary images by their coordinates. Close centers form one group that corresponds to one blob, which is controlled by the MinDistBetweenBlobs parameter.
From the groups, estimate final centers of blobs and their radiuses and return as locations and sizes of keypoints.

This class performs several filtrations of returned blobs. You should set FilterBy* to true/false to turn on/off corresponding filtration. Available filtrations:

By color. This filter compares the intensity of a binary image at the center of a blob to BlobColor. If they differ, the blob is filtered out. Use BlobColor = 0 to extract dark blobs and BlobColor = 255 to extract light blobs.
By area. Extracted blobs have an area between MinArea (inclusive) and MaxArea (exclusive).
By circularity. Extracted blobs have circularity ((4*pi*area)/(perimeter*perimeter)) between MinCircularity (inclusive) and MaxCircularity (exclusive).
By ratio of the minimum inertia to maximum inertia. Extracted blobs have this ratio between MinInertiaRatio (inclusive) and MaxInertiaRatio (exclusive).
By convexity. Extracted blobs have convexity (area / area of blob convex hull) between MinConvexity (inclusive) and MaxConvexity (exclusive).

Default values of parameters are tuned to extract dark circular blobs.

Superclasses	handle
Sealed	false
Construct on load	false

	addlistener	Add listener for event.
	clear	Clears the algorithm state
	delete	Destructor
	detect	Detects keypoints in an image or image set
	empty	Checks if detector object is empty
	eq	== (EQ) Test handle equality.
	findobj	Find objects matching specified conditions.
	findprop	Find property of MATLAB handle object.
	ge	>= (GE) Greater than or equal relation for handles.
	getDefaultName	Returns the algorithm string identifier
	gt	> (GT) Greater than relation for handles.
Sealed	isvalid	Test handle validity.
	le	<= (LE) Less than or equal relation for handles.
	listener	Add listener for event without binding the listener to the source object.
	load	Loads algorithm from a file or a string
	lt	< (LT) Less than relation for handles.
	ne	~= (NE) Not equal relation for handles.
	notify	Notify listeners of event.
	save	Saves the algorithm parameters to a file
	typeid	Name of the C++ type (RTTI)