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# vigra/gaborfilter.hxx

    00001 /************************************************************************/
    00002 /*                                                                      */
    00003 /*         Copyright 2002-2004 by Ullrich Koethe and Hans Meine         */
    00004 /*       Cognitive Systems Group, University of Hamburg, Germany        */
    00005 /*                                                                      */
    00006 /*    This file is part of the VIGRA computer vision library.           */
    00007 /*    ( Version 1.6.0, Aug 13 2008 )                                    */
    00008 /*    The VIGRA Website is                                              */
    00009 /*        http://kogs-www.informatik.uni-hamburg.de/~koethe/vigra/      */
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    00011 /*        ullrich.koethe@iwr.uni-heidelberg.de    or                    */
    00012 /*        vigra@informatik.uni-hamburg.de                               */
    00013 /*                                                                      */
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    00022 /*                                                                      */
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    00025 /*    Software.                                                         */
    00026 /*                                                                      */
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    00035 /*                                                                      */
    00036 /************************************************************************/
    00037
    00038
    00039 #ifndef VIGRA_GABORFILTER_HXX
    00040 #define VIGRA_GABORFILTER_HXX
    00041
    00042 #include "imagecontainer.hxx"
    00043 #include "config.hxx"
    00044 #include "stdimage.hxx"
    00045 #include "copyimage.hxx"
    00046 #include "transformimage.hxx"
    00047 #include "combineimages.hxx"
    00048 #include "utilities.hxx"
    00049
    00050 #include <functional>
    00051 #include <vector>
    00052 #include <cmath>
    00053
    00054 namespace vigra {
    00055
    00056 /** \addtogroup GaborFilter Gabor Filter
    00057     Functions to create or apply gabor filter (latter based on FFTW).
    00058 */
    00059 //@{
    00060
    00061 /********************************************************/
    00062 /*                                                      */
    00063 /*                   createGaborFilter                  */
    00064 /*                                                      */
    00065 /********************************************************/
    00066
    00067 /** \brief Create a gabor filter in frequency space.
    00068
    00069     The orientation is given in radians, the other parameters are the
    00070     center frequency (for example 0.375 or smaller) and the two
    00071     angular and radial sigmas of the gabor filter. (See \ref
    00072     angularGaborSigma() for an explanation of possible values.)
    00073
    00074     The energy of the filter is explicitely normalized to 1.0.
    00075
    00076     <b> Declarations:</b>
    00077
    00078     pass arguments explicitly:
    00079     \code
    00080     namespace vigra {
    00081         template <class DestImageIterator, class DestAccessor>
    00082         void createGaborFilter(DestImageIterator destUpperLeft,
    00083                                DestImageIterator destLowerRight,
    00084                                DestAccessor da,
    00085                                double orientation, double centerFrequency,
    00086                                double angularSigma, double radialSigma)
    00087     }
    00088     \endcode
    00089
    00090     use argument objects in conjunction with \ref ArgumentObjectFactories :
    00091     \code
    00092     namespace vigra {
    00093         template <class DestImageIterator, class DestAccessor>
    00094         void createGaborFilter(triple<DestImageIterator,
    00095                                       DestImageIterator,
    00096                                       DestAccessor> dest,
    00097                                double orientation, double centerFrequency,
    00098                                double angularSigma, double radialSigma)
    00099     }
    00100     \endcode
    00101
    00102     <b> Usage:</b>
    00103
    00104     <b>\#include</b> <<a href="gaborfilter_8hxx-source.html">vigra/gaborfilter.hxx</a>><br>
    00105
    00106     Namespace: vigra
    00107
    00108     \code
    00109     vigra::FImage gabor(w,h);
    00110
    00111     vigra::createGaborFilter(destImageRange(gabor), orient, freq,
    00112                              angularGaborSigma(directionCount, freq)
    00113                              radialGaborSigma(freq));
    00114     \endcode
    00115 */
    00116 doxygen_overloaded_function(template <...> void createGaborFilter)
    00117
    00118 template <class DestImageIterator, class DestAccessor>
    00119 void createGaborFilter(DestImageIterator destUpperLeft,
    00120                        DestImageIterator destLowerRight, DestAccessor da,
    00121                        double orientation, double centerFrequency,
    00122                        double angularSigma, double radialSigma)
    00123 {
    00124     int w= destLowerRight.x - destUpperLeft.x;
    00125     int h= destLowerRight.y - destUpperLeft.y;
    00126
    00127     double squaredSum = 0.0;
    00128     double cosTheta= VIGRA_CSTD::cos(orientation);
    00129     double sinTheta= VIGRA_CSTD::sin(orientation);
    00130
    00131     double radialSigma2 = radialSigma*radialSigma;
    00132     double angularSigma2 = angularSigma*angularSigma;
    00133
    00134     double wscale = w % 1 ?
    00135                     1.0f / (w-1) :
    00136                     1.0f / w;
    00137     double hscale = h % 1 ?
    00138                     1.0f / (h-1) :
    00139                     1.0f / h;
    00140
    00141     int dcX= (w+1)/2, dcY= (h+1)/2;
    00142
    00143     double u, v;
    00144     for ( int y=0; y<h; y++, destUpperLeft.y++ )
    00145     {
    00146         typename DestImageIterator::row_iterator dix = destUpperLeft.rowIterator();
    00147
    00148         v = hscale * ((h - (y - dcY))%h - dcY);
    00149         for ( int x=0; x<w; x++, dix++ )
    00150         {
    00151             u= wscale*((x - dcX + w)%w - dcX);
    00152
    00153             double uu = cosTheta*u + sinTheta*v - centerFrequency;
    00154             double vv = -sinTheta*u + cosTheta*v;
    00155             double gabor;
    00156
    00157             gabor = VIGRA_CSTD::exp(-0.5*(uu*uu / radialSigma2 + vv*vv / angularSigma2));
    00158             squaredSum += gabor * gabor;
    00159             da.set( gabor, dix );
    00160         }
    00161     }
    00162     destUpperLeft.y -= h;
    00163
    00164     // clear out DC value and remove it from the squared sum
    00165     double dcValue = da(destUpperLeft);
    00166     squaredSum -= dcValue * dcValue;
    00167     da.set( 0.0, destUpperLeft );
    00168
    00169     // normalize energy to one
    00170     double factor = VIGRA_CSTD::sqrt(squaredSum);
    00171     for ( int y=0; y<h; y++, destUpperLeft.y++ )
    00172     {
    00173         typename DestImageIterator::row_iterator dix = destUpperLeft.rowIterator();
    00174
    00175         for ( int x=0; x<w; x++, dix++ )
    00176         {
    00177             da.set( da(dix) / factor, dix );
    00178         }
    00179     }
    00180 }
    00181
    00182 template <class DestImageIterator, class DestAccessor>
    00183 inline
    00184 void createGaborFilter(triple<DestImageIterator, DestImageIterator,
    00185                               DestAccessor> dest,
    00186                               double orientation, double centerFrequency,
    00187                               double angularSigma, double radialSigma)
    00188 {
    00189     createGaborFilter(dest.first, dest.second, dest.third,
    00190                       orientation, centerFrequency,
    00191                       angularSigma, radialSigma);
    00192 }
    00193
    00194 /********************************************************/
    00195 /*                                                      */
    00196 /*                   radialGaborSigma                   */
    00197 /*                                                      */
    00198 /********************************************************/
    00199
    00200 /** \brief Calculate sensible radial sigma for given parameters.
    00201
    00202     For a brief introduction what is meant with "sensible" sigmas, see
    00203     \ref angularGaborSigma().
    00204
    00205     <b> Declaration:</b>
    00206
    00207     \code
    00208     namespace vigra {
    00209         double radialGaborSigma(double centerFrequency)
    00210     }
    00211     \endcode
    00212  */
    00213
    00214 inline double radialGaborSigma(double centerFrequency)
    00215 {
    00216     static double sfactor = 3.0 * VIGRA_CSTD::sqrt(VIGRA_CSTD::log(4.0));
    00217     return centerFrequency / sfactor;
    00218 }
    00219
    00220 /********************************************************/
    00221 /*                                                      */
    00222 /*                   angularGaborSigma                  */
    00223 /*                                                      */
    00224 /********************************************************/
    00225
    00226 /** \brief Calculate sensible angular sigma for given parameters.
    00227
    00228     "Sensible" means: If you use a range of gabor filters for feature
    00229     detection, you are interested in minimal redundance. This is hard
    00230     to define but one possible try is to arrange the filters in
    00231     frequency space, so that the half-peak-magnitude ellipses touch
    00232     each other.
    00233
    00234     To do so, you must know the number of directions (first parameter
    00235     for the angular sigma function) and the center frequency of the
    00236     filter you want to calculate the sigmas for.
    00237
    00238     The exact formulas are:
    00239     \code
    00240     sigma_radial= 1/sqrt(ln(4)) * centerFrequency/3
    00241     \endcode
    00242
    00243     \code
    00244     sigma_angular= 1/sqrt(ln(4)) * tan(pi/(directions*2))
    00245                    * sqrt(8/9) * centerFrequency
    00246     \endcode
    00247
    00248     <b> Declaration:</b>
    00249
    00250     \code
    00251     namespace vigra {
    00252         double angularGaborSigma(int directionCount, double centerFrequency)
    00253     }
    00254     \endcode
    00255  */
    00256
    00257 inline double angularGaborSigma(int directionCount, double centerFrequency)
    00258 {
    00259     return VIGRA_CSTD::tan(M_PI/directionCount/2.0) * centerFrequency
    00260         * VIGRA_CSTD::sqrt(8.0 / (9 * VIGRA_CSTD::log(4.0)));
    00261 }
    00262
    00263 /********************************************************/
    00264 /*                                                      */
    00265 /*                   GaborFilterFamily                  */
    00266 /*                                                      */
    00267 /********************************************************/
    00268
    00269 /** \brief Family of gabor filters of different scale and direction.
    00270
    00271     A GaborFilterFamily can be used to quickly create a whole family
    00272     of gabor filters in frequency space. Especially useful in
    00273     conjunction with \ref applyFourierFilterFamily, since it's derived
    00274     from \ref ImageArray.
    00275
    00276     The filter parameters are chosen to make the center frequencies
    00277     decrease in octaves with increasing scale indices, and to make the
    00278     half-peak-magnitude ellipses touch each other to somewhat reduce
    00279     redundancy in the filter answers. This is done by using \ref
    00280     angularGaborSigma() and \ref radialGaborSigma(), you'll find more
    00281     information there.
    00282
    00283     The template parameter ImageType should be a scalar image type suitable for filling in
    00284
    00285     <b>\#include</b> <<a href="gaborfilter_8hxx-source.html">vigra/gaborfilter.hxx</a>>
    00286
    00287     Namespace: vigra
    00288 */
    00289 template <class ImageType,
    00290       class Alloc = typename ImageType::allocator_type::template rebind<ImageType>::other >
    00291 class GaborFilterFamily
    00292 : public ImageArray<ImageType, Alloc>
    00293 {
    00294     typedef ImageArray<ImageType, Alloc> ParentClass;
    00295     int scaleCount_, directionCount_;
    00296     double maxCenterFrequency_;
    00297
    00298 protected:
    00299     void initFilters()
    00300     {
    00301         for(int direction= 0; direction<directionCount_; direction++)
    00302             for(int scale= 0; scale<scaleCount_; scale++)
    00303             {
    00304                 double angle = direction * M_PI / directionCount();
    00305                 double centerFrequency =
    00306                     maxCenterFrequency_ / VIGRA_CSTD::pow(2.0, (double)scale);
    00307                 createGaborFilter(destImageRange(this->images_[filterIndex(direction, scale)]),
    00308                                   angle, centerFrequency,
    00309                                   angularGaborSigma(directionCount(), centerFrequency),
    00310                                   radialGaborSigma(centerFrequency));
    00311             }
    00312     }
    00313
    00314 public:
    00315     enum { stdFilterSize= 128, stdDirectionCount= 6, stdScaleCount= 4 };
    00316
    00317         /** Constructs a family of gabor filters in frequency
    00318             space. The filters will be calculated on construction, so
    00319             it makes sense to provide good parameters right now
    00320             although they can be changed later, too. If you leave them
    00321             out, the defaults are a \ref directionCount of 6, a \ref
    00322             scaleCount of 4 and a \ref maxCenterFrequency of
    00323             3/8(=0.375).
    00324         */
    00325     GaborFilterFamily(const Diff2D & size,
    00326                       int directionCount = stdDirectionCount, int scaleCount = stdScaleCount,
    00327                       double maxCenterFrequency = 3.0/8.0,
    00328                       Alloc const & alloc = Alloc())
    00329         : ParentClass(directionCount*scaleCount, size, alloc),
    00330           scaleCount_(scaleCount),
    00331           directionCount_(directionCount),
    00332           maxCenterFrequency_(maxCenterFrequency)
    00333     {
    00334         initFilters();
    00335     }
    00336
    00337         /** Convenience variant of the above constructor taking width
    00338             and height separately. Also, this one serves as default
    00339             constructor constructing 128x128 pixel filters.
    00340          */
    00341     GaborFilterFamily(int width= stdFilterSize, int height= -1,
    00342                       int directionCount = stdDirectionCount, int scaleCount = stdScaleCount,
    00343                       double maxCenterFrequency = 3.0/8.0,
    00344                       Alloc const & alloc = Alloc())
    00345         : ParentClass(directionCount*scaleCount,
    00346                       Size2D(width, height > 0 ? height : width), alloc),
    00347           scaleCount_(scaleCount),
    00348           directionCount_(directionCount),
    00349           maxCenterFrequency_(maxCenterFrequency)
    00350     {
    00351         initFilters();
    00352     }
    00353
    00354         /** Return the index of the filter with the given direction and
    00355             scale in this ImageArray. direction must in the range
    00356             0..directionCount()-1 and scale in the range
    00357             0..rangeCount()-1. This is useful for example if you used
    00358             \ref applyFourierFilterFamily() and got a resulting
    00359             ImageArray which still has the same order of images, but no
    00360             \ref getFilter() method anymore.
    00361          */
    00362     int filterIndex(int direction, int scale) const
    00363     {
    00364         return scale*directionCount()+direction;
    00365     }
    00366
    00367         /** Return the filter with the given direction and
    00368             scale. direction must in the range 0..directionCount()-1
    00369             and scale in the range 0..rangeCount()-1.
    00370             <tt>filters.getFilter(direction, scale)</tt> is the same as
    00371             <tt>filters[filterIndex(direction, scale)]</tt>.
    00372          */
    00373     ImageType const & getFilter(int direction, int scale) const
    00374     {
    00375         return this->images_[filterIndex(direction, scale)];
    00376     }
    00377
    00378         /** Resize all filters (causing their recalculation).
    00379          */
    00380     virtual void resizeImages(const Diff2D &newSize)
    00381     {
    00382         ParentClass::resizeImages(newSize);
    00383         initFilters();
    00384     }
    00385
    00386         /** Query the number of filter scales available.
    00387          */
    00388     int scaleCount() const
    00389         { return scaleCount_; }
    00390
    00391         /** Query the number of filter directions available.
    00392          */
    00393     int directionCount() const
    00394         { return directionCount_; }
    00395
    00396         /** Change the number of directions / scales. This causes the
    00397             recalculation of all filters.
    00398          */
    00399     void setDirectionScaleCounts(int directionCount, int scaleCount)
    00400     {
    00401         this->resize(directionCount * scaleCount);
    00402         scaleCount_ = scaleCount;
    00403         directionCount_ = directionCount;
    00404         initFilters();
    00405     }
    00406
    00407         /** Return the center frequency of the filter(s) with
    00408             scale==0. Filters with scale>0 will have a center frequency
    00409             reduced in octaves:
    00410             <tt>centerFrequency= maxCenterFrequency / 2.0^scale</tt>
    00411         */
    00412     double maxCenterFrequency()
    00413         { return maxCenterFrequency_; }
    00414
    00415         /** Change the center frequency of the filter(s) with
    00416             scale==0. See \ref maxCenterFrequency().
    00417          */
    00418     void setMaxCenterFrequency(double maxCenterFrequency)
    00419     {
    00420         maxCenterFrequency_ = maxCenterFrequency;
    00421         initFilters();
    00422     }
    00423 };
    00424
    00425 //@}
    00426
    00427 } // namespace vigra
    00428
    00429 #endif // VIGRA_GABORFILTER_HXX

© Ullrich Köthe (ullrich.koethe@iwr.uni-heidelberg.de) Heidelberg Collaboratory for Image Processing, University of Heidelberg, Germany | html generated using doxygen and Python VIGRA 1.6.0 (13 Aug 2008)