Otsu Threshold computation

scalar =	otsuThreshold (inImg)
scalar =	otsuThreshold (inImg,histogram)

Detailed Description

Computation of the binary threshold on one image, using Otsu method.

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.

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
    otsuThresholdValue = bin.otsuThreshold(inImg)

Example of C++ code :

Example informations

Header file

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

Code Example

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

        // Sample calculating automatically the histogram
        // ----------------------------------------------

        // compute otsu threshold associated to input image
        ipReal64 outThresholdValue = otsuThreshold(pInImg);

        // Sample with the histogram as input parameter
        // ----------------------------------------------

        // Set the histogram parameters
        const ipReal64 min = 50.;
        const ipReal64 max = 250.;
        const ipReal64 fBinWidth = 2.;
        HistoMsrParamsPtr pHistoPrms = createHistoMsrParamsWithBinWidth(min, max, fBinWidth);

        // Compute the histogram
        HistogramDataPtr pHistogramData = histogramMsr(pInImg, pHistoPrms);

        // compute otsu threshold associated to input image
        ipReal64 outThresholdValue_manualHisto = otsuThreshold(pInImg, pHistogramData);