Otsu Threshold binarizationSee full documentation

outImg,outThreshold =	otsuThresholdImg (inImg)
scalar =	otsuThresholdImg (inImg,outBinImg)
outImg,outThreshold =	otsuThresholdImg (inImg,histogram)
scalar =	otsuThresholdImg (inImg,histogram,outBinImg)

Detailed Description

Compute the Otsu threshold of an input image, and binarize the image using this threshold.

Otsu's method is used to automatically perform the binarization of an input image. It assumes that the image is bi-modal (pixel intensities can be distinguished in 2 classes: background pixels and foreground pixels). It then calculates the optimal threshold that separates these 2 classes, by minimizing their intra-class variance. In this implementation, the alternate method (maximizing the inter-classes variance) is used. It has the advantage to be faster than the first method.

See also

http://en.wikipedia.org/w/index.php?title=Otsu%27s_method&oldid=617320940 for more details.

On output, binarized image values are given by:

with the threshold computed from Otsu's method.

Input and output images must have same size and buffer type.

Here is an example of automatic otsu image thresholding applied to a 8-bits grey level image (on ouput, computed threshold equals 118) :

Example of Python code :

Example imports

import PyIPSDK
import PyIPSDK.IPSDKIPLBinarization as bin

Code Example

    # opening of input images
    inImg = PyIPSDK.loadTiffImageFile(inputImgPath)    
    
    # otsu threshold computation
    outImg,  otsuThresholdValue = bin.otsuThresholdImg(inImg)

Example of C++ code :

Example informations

Header file

#include <IPSDKIPL/IPSDKIPLBinarization/Processor/OtsuThresholdImg/OtsuThresholdImg.h>

Code Example

        // open input image
        ImageGeometryPtr pInputImageGeometry = geometry2d(inType, sizeX, sizeY);
        ImagePtr pInImg = loadRawImageFile(inPath, *pInputImageGeometry);

        // Sample with a generated output image
        // ------------------------------------

        // compute thresholded output image
        OtsuResult otsuResult = otsuThresholdImg(pInImg);

        // Sample with a provided output image
        // -----------------------------------

        // create output image
        ImageGeometryPtr pOutputImageGeometry = geometry2d(eImageBufferType::eIBT_Binary, sizeX, sizeY);
        boost::shared_ptr<MemoryImage> pOutImg(boost::make_shared<MemoryImage>());
        pOutImg->init(*pOutputImageGeometry);

        // compute thresholded output image
        ipReal64 fOutThreshold = otsuThresholdImg(pInImg, pOutImg);