OpenCV  3.2.0 Open Source Computer Vision
Extended Image Processing

## Modules

Structured forests for fast edge detection

Filters

Superpixels

Image segmentation

Fast line detector

## Functions

void cv::ximgproc::niBlackThreshold (InputArray _src, OutputArray _dst, double maxValue, int type, int blockSize, double delta)
Applies Niblack thresholding to input image. More...

void cv::ximgproc::thinning (InputArray src, OutputArray dst, int thinningType=THINNING_ZHANGSUEN)
Applies a binary blob thinning operation, to achieve a skeletization of the input image. More...

## § niBlackThreshold()

 void cv::ximgproc::niBlackThreshold ( InputArray _src, OutputArray _dst, double maxValue, int type, int blockSize, double delta )

Applies Niblack thresholding to input image.

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.

The threshold value $$T(x, y)$$ is the mean minus $$delta$$ times standard deviation of $$\texttt{blockSize} \times\texttt{blockSize}$$ neighborhood of $$(x, y)$$.

The function can't process the image in-place.

Parameters
 _src Source 8-bit single-channel image. _dst 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, used with the THRESH_BINARY and THRESH_BINARY_INV thresholding types. type Thresholding type, see cv::ThresholdTypes. blockSize Size of a pixel neighborhood that is used to calculate a threshold value for the pixel: 3, 5, 7, and so on. delta Constant multiplied with the standard deviation and subtracted from the mean. Normally, it is taken to be a real number between 0 and 1.
 void cv::ximgproc::thinning ( InputArray src, OutputArray dst, int thinningType = THINNING_ZHANGSUEN )