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/**
\page tutorial-imgproc-autothreshold Tutorial: Automatic thresholding
\tableofcontents
\section imgproc_autothreshold_intro Introduction
This tutorial will show you how to automatically threshold, binarize an image using different methods:
- Huang \cite Huang_imagethresholding
- Intermodes \cite NYAS:NYAS1035
- Isodata \cite article4310039
- Mean \cite Glasbey:1993:AHT:167725.167747
- Otsu \cite article4310076
- Triangle \cite doi:10.1177/25.7.70454
These functions have been ported from the <a href="https://imagej.net/Auto_Threshold">Auto Threshold ImageJ plugin</a> and you can refer to the corresponding documentation for more information.
\section imgproc_autothreshold_example Example code
The following example also available in tutorial-autothreshold.cpp will demonstrate on a sample image the result of each of these methods:
\include tutorial-autothreshold.cpp
These functions are provided in a \a vp:: namespace and accessible using this include:
\snippet tutorial-autothreshold.cpp Include
The code to use is pretty straightword:
- Huang:
\snippet tutorial-autothreshold.cpp Huang
- Intermodes:
\snippet tutorial-autothreshold.cpp Intermodes
- IsoData:
\snippet tutorial-autothreshold.cpp IsoData
- Mean:
\snippet tutorial-autothreshold.cpp Mean
- Otsu:
\snippet tutorial-autothreshold.cpp Otsu
- Triangle:
\snippet tutorial-autothreshold.cpp Triangle
The following image presents the results for each method:
\image html img-tutorial-autothreshold.png "Comparison of different binarizations using the threshold value returned by each method"
The function vp::autoThreshold(vpImage<unsigned char> &, const vp::vpAutoThresholdMethod &, const unsigned char, const unsigned char) has two parameters to specify the pixel values to use for the background and the foreground. By default, it is (see vpImageTools::binarise(vpImage<Type> &, Type, Type, Type, Type, Type, const bool)):
\f[
I_{bin}\left ( i,j \right ) =
\left \{ \begin{matrix}
0 \text{ if } I_{src}\left ( i,j \right ) < \text{threshold} \\
255 \text{ otherwise}
\end{matrix} \right.
\f]
\section imgproc_autothreshold_next Next tutorial
You can now read the \ref tutorial-imgproc-contour, to learn how to extract the contours from a binary image.
*/
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