SimpleBlobDetector
import { SimpleBlobDetector } from '@banou/opencv-wasm'Use after await initOpenCV(). See the initialization and named imports guide.
Native object: release it with using or delete(). Factories can return null; check before calling methods. Inherits Feature2D.
HAVE_OPENCV_DNN || CV_DOXYGEN 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 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
(
\frac{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.
Constructors and members
static create
Flag to enable contour collection. If set to true, the detector will store the contours of the detected blobs in memory, which can be retrieved after the detect() call using getBlobContours().
Note: Default value is false.
create(parameters: SimpleBlobDetector_Params): SimpleBlobDetector | null;2 available overloads
create(): SimpleBlobDetector | null;create(parameters: SimpleBlobDetector_Params): SimpleBlobDetector | null;parametersparameters argument (SimpleBlobDetector_Params).
The SimpleBlobDetector | null result.
clone
Create another handle to the same native object. This retains the object without copying its pixels or algorithm state; dispose both handles separately.
clone(): this;The this result.
getDefaultName
Returns the algorithm string identifier. This string is used as top level xml/yml node tag when the object is saved to a file or string.
getDefaultName(): string;The string result.
getBlobContours
Returns the contours of the blobs detected during the last call to detect().
Note: The Params::collectContours parameter must be set to true before calling
detect() for this method to return any data.
getBlobContours(): PointVectorVector;The PointVectorVector result. Release returned native handles with using or delete(), including handles nested in results.
setParams
Set the params used by this SimpleBlobDetector object.
setParams(params: SimpleBlobDetector_Params): void;paramsparams argument (SimpleBlobDetector_Params).
getParams
Return the params configured on this SimpleBlobDetector object.
getParams(): SimpleBlobDetector_Params;The SimpleBlobDetector_Params result.
These signatures describe this package. Upstream documentation can mention optional backends that are absent from this build. Check runtime compatibility before choosing a backend or file format.