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watershed.cxx

Segment image by means of the watershed algorithm, using seededRegionGrowing()
Usage: watershed infile outfile

/************************************************************************/
/* */
/* Copyright 1998-2002 by Ullrich Koethe */
/* */
/* This file is part of the VIGRA computer vision library. */
/* The VIGRA Website is */
/* http://hci.iwr.uni-heidelberg.de/vigra/ */
/* Please direct questions, bug reports, and contributions to */
/* ullrich.koethe@iwr.uni-heidelberg.de or */
/* vigra@informatik.uni-hamburg.de */
/* */
/* Permission is hereby granted, free of charge, to any person */
/* obtaining a copy of this software and associated documentation */
/* files (the "Software"), to deal in the Software without */
/* restriction, including without limitation the rights to use, */
/* copy, modify, merge, publish, distribute, sublicense, and/or */
/* sell copies of the Software, and to permit persons to whom the */
/* Software is furnished to do so, subject to the following */
/* conditions: */
/* */
/* The above copyright notice and this permission notice shall be */
/* included in all copies or substantial portions of the */
/* Software. */
/* */
/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND */
/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES */
/* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND */
/* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT */
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/* */
/************************************************************************/
#include <iostream>
#include "vigra/stdimage.hxx"
#include "vigra/stdimagefunctions.hxx"
#include "vigra/localminmax.hxx"
#include "vigra/labelimage.hxx"
#include "vigra/seededregiongrowing.hxx"
#include "vigra/impex.hxx"
using namespace vigra;
// define a functor that calsulates the squared magnitude of the gradient
// given the x- and y- components of the gradient
struct GradientSquaredMagnitudeFunctor
{
float operator()(float const & g1, float const & g2) const
{
return g1 * g1 + g2 * g2;
}
float operator()(vigra::RGBValue<float> const & rg1, vigra::RGBValue<float> const & rg2) const
{
float g1 = rg1.squaredMagnitude();
float g2 = rg2.squaredMagnitude();
return g1 + g2;
}
};
// generic implementation of the watershed algorithm
template <class InImage, class OutImage>
void watershedSegmentation(InImage & in, OutImage & out, double scale)
{
typedef typename vigra::NumericTraits<typename InImage::value_type>::RealPromote
TmpType;
int w = in.width();
int h = in.height();
vigra::BasicImage<TmpType> gradientx(w, h);
vigra::BasicImage<TmpType> gradienty(w, h);
vigra::FImage gradientmag(w, h);
// calculate the x- and y-components of the image gradient at given scale
recursiveFirstDerivativeX(srcImageRange(in), destImage(gradientx), scale);
recursiveSmoothY(srcImageRange(gradientx), destImage(gradientx), scale);
recursiveFirstDerivativeY(srcImageRange(in), destImage(gradienty), scale);
recursiveSmoothX(srcImageRange(gradienty), destImage(gradienty), scale);
// transform components into gradient magnitude
combineTwoImages(srcImageRange(gradientx), srcImage(gradienty),
destImage(gradientmag), GradientSquaredMagnitudeFunctor());
vigra::IImage labels(w, h);
labels = 0;
// find the local minima of the gradient magnitude
// (might be larger than one pixel)
extendedLocalMinima(srcImageRange(gradientmag), destImage(labels), 1);
// label the minima just found
int max_region_label =
labelImageWithBackground(srcImageRange(labels), destImage(labels),
false, 0);
// create a statistics functor for region growing
gradstat(max_region_label);
// perform region growing, starting from the minima of the gradient magnitude;
// as the feature (first input) image contains the gradient magnitude,
// this calculates the catchment basin of each minimum
seededRegionGrowing(srcImageRange(gradientmag), srcImage(labels),
destImage(labels), gradstat);
// initialize a functor to determine the average gray-value or color
// for each region (catchment basin) just found
averages(max_region_label);
// calculate the averages
inspectTwoImages(srcImageRange(in), srcImage(labels), averages);
// write the averages into the destination image (the functor 'averages'
// acts as a look-up table)
transformImage(srcImageRange(labels), destImage(out), averages);
// mark the watersheds (region boundaries) black
regionImageToEdgeImage(srcImageRange(labels), destImage(out),
vigra::NumericTraits<typename OutImage::value_type>::zero());
}
int main(int argc, char ** argv)
{
if(argc != 3)
{
std::cout << "Usage: " << argv[0] << " infile outfile" << std::endl;
std::cout << "(supported formats: " << vigra::impexListFormats() << ")" << std::endl;
return 1;
}
try
{
vigra::ImageImportInfo info(argv[1]);
// input width of gradient filter
double scale = 1.0;
std::cout << "Scale for gradient calculation ? ";
std::cin >> scale;
if(info.isGrayscale())
{
int w = info.width();
int h = info.height();
vigra::BImage in(w, h);
importImage(info, destImage(in));
vigra::BImage out(w, h);
// perform watershed segmentation on gray image
// note that the watershed algorithm usually results in an
// oversegmentation (i.e., too many regions), but its boundary
// localization is quite good
watershedSegmentation(in, out, scale);
std::cout << "Writing " << argv[2] << std::endl;
exportImage(srcImageRange(out), vigra::ImageExportInfo(argv[2]));
}
else
{
int w = info.width();
int h = info.height();
vigra::BRGBImage in(w, h);
importImage(info, destImage(in));
vigra::BRGBImage out(w, h);
// perform watershed segmentation on color image
// note that the watershed algorithm usually results in an
// oversegmentation (i.e., too many regions), but its boundary
// localization is quite good
watershedSegmentation(in, out, scale);
std::cout << "Writing " << argv[2] << std::endl;
exportImage(srcImageRange(out), vigra::ImageExportInfo(argv[2]));
}
}
catch (vigra::StdException & e)
{
std::cout << e.what() << std::endl;
return 1;
}
return 0;
}

© Ullrich Köthe (ullrich.koethe@iwr.uni-heidelberg.de)
Heidelberg Collaboratory for Image Processing, University of Heidelberg, Germany

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