adaptiveThreshold

Image processingfunctionOpenCV 5.0.0

import { adaptiveThreshold } from '@banou/opencv-wasm'

Use after await initOpenCV(). See the initialization and named imports guide.

Explore visually: Adaptive thresholding →

Compute a different intensity threshold for each local neighbourhood.

VISUAL WALKTHROUGHSegmentation

REFERENCE INPUTObject under uneven lighting

The same scene stays here while the working view changes.

→

RESULTBinary selection mask

336 of 384 pixels pass the rule. The mask records membership, not the original brightness.

Computed teaching example on a 24 × 16 image. Small kernels and simplified settings keep each change visible; use the image laboratory for native OpenCV.

Applies an adaptive threshold to an array.

The function transforms a grayscale image to a binary image according to the formulae:

• THRESH_BINARY

dst(x,y) =  \fork{\texttt{maxValue}}{if \(src(x,y) > T(x,y)\)}{0}{otherwise}

• THRESH_BINARY_INV

dst(x,y) =  \fork{0}{if \(src(x,y) > T(x,y)\)}{\texttt{maxValue}}{otherwise}

where T(x,y) is a threshold calculated individually for each pixel (see adaptiveMethod parameter).

The function can process the image in-place.

See: threshold, blur, GaussianBlur

adaptiveThreshold(src: Mat, dst: Mat, maxValue: number, adaptiveMethod: number, thresholdType: number, blockSize: number, C: number): void;

src

Source 8-bit single-channel image.

dst

Output destination, filled by the native operation. Destination image of the same size and the same type as src.

maxValue

Non-zero value assigned to the pixels for which the condition is satisfied

adaptiveMethod

Adaptive thresholding algorithm to use, see #AdaptiveThresholdTypes. The #BORDER_REPLICATE | #BORDER_ISOLATED is used to process boundaries.

thresholdType

Thresholding type that must be either #THRESH_BINARY or #THRESH_BINARY_INV, see #ThresholdTypes.

blockSize

Size of a pixel neighborhood that is used to calculate a threshold value for the pixel: 3, 5, 7, and so on.

C

Constant subtracted from the mean or weighted mean (see the details below). Normally, it is positive but may be zero or negative as well.

Upstream declaration ↗

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.