[ VIGRA Homepage | Class Index | Function Index | File Index | Main Page ]

| vigra/interpolating_accessor.hxx |
--- | --- | ---

    00001 /************************************************************************/
    00002 /*                                                                      */
    00003 /*               Copyright 1998-2002 by Ullrich Koethe                  */
    00004 /*       Cognitive Systems Group, University of Hamburg, Germany        */
    00005 /*                                                                      */
    00006 /*    This file is part of the VIGRA computer vision library.           */
    00007 /*    ( Version 1.3.2, Jan 27 2005 )                                    */
    00008 /*    You may use, modify, and distribute this software according       */
    00009 /*    to the terms stated in the LICENSE file included in               */
    00010 /*    the VIGRA distribution.                                           */
    00011 /*                                                                      */
    00012 /*    The VIGRA Website is                                              */
    00013 /*        http://kogs-www.informatik.uni-hamburg.de/~koethe/vigra/      */
    00014 /*    Please direct questions, bug reports, and contributions to        */
    00015 /*        koethe@informatik.uni-hamburg.de                              */
    00016 /*                                                                      */
    00017 /*  THIS SOFTWARE IS PROVIDED AS IS AND WITHOUT ANY EXPRESS OR          */
    00018 /*  IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED      */
    00019 /*  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. */
    00020 /*                                                                      */
    00021 /************************************************************************/
    00022
    00023 #ifndef VIGRA_INTERPOLATING_ACCESSOR_HXX
    00024 #define VIGRA_INTERPOLATING_ACCESSOR_HXX
    00025
    00026
    00027 #include "vigra/accessor.hxx"
    00028 #include "vigra/diff2d.hxx"
    00029
    00030 namespace vigra {
    00031
    00032 /** \addtogroup DataAccessors
    00033 */
    00034 //@{
    00035
    00036 /********************************************************/
    00037 /*                                                      */
    00038 /*            BilinearInterpolatingAccessor             */
    00039 /*                                                      */
    00040 /********************************************************/
    00041
    00042 /** \brief Bilinear interpolation at non-integer positions.
    00043
    00044     This accessor allows an image be accessed at arbitrary non-integer
    00045     coordinates and performs an bi-linear interpolation to
    00046     obtain a pixel value.
    00047     It uses the given ACCESSOR (which is usually the
    00048     accessor originally associated with the iterator)
    00049     to access data.
    00050
    00051     <b>\#include</b> "<a href="accessor_8hxx-source.html">vigra/accessor.hxx</a>"
    00052     Namespace: vigra
    00053
    00054     <b> Required Interface:</b>
    00055
    00056     \code
    00057     ITERATOR iter;
    00058     ACCESSOR a;
    00059     VALUETYPE destvalue;
    00060     float s;
    00061     int x, y;
    00062
    00063     destvalue = s * a(iter, x, y) + s * a(iter, x, y);
    00064
    00065     \endcode
    00066 */
    00067 template <class ACCESSOR, class VALUETYPE>
    00068 class BilinearInterpolatingAccessor
    00069 {
    00070   public:
    00071     /** the iterators' pixel type
    00072     */
    00073     typedef VALUETYPE value_type;
    00074
    00075     /** init from given accessor
    00076     */
    00077     BilinearInterpolatingAccessor(ACCESSOR a)
    00078     : a_(a)
    00079     {}
    00080
    00081     /** Interpolate the data item at a non-integer position.
    00082         Ensure that no outside pixels are accessed if
    00083         (x, y) is near the image border (as long as
    00084         0 <= x <= width-1, 0 <= y <= height-1).
    00085     */
    00086     template <class ITERATOR>
    00087     value_type operator()(ITERATOR const & i, float x, float y) const
    00088     {
    00089         int ix = int(x);
    00090         int iy = int(y);
    00091         float dx = x - ix;
    00092         float dy = y - iy;
    00093
    00094         value_type ret;
    00095
    00096         // avoid dereferencing the iterator outside its range
    00097         if(dx == 0.0)
    00098         {
    00099             if(dy == 0.0)
    00100             {
    00101                 ret = a_(i, Diff2D(ix, iy));
    00102             }
    00103             else
    00104             {
    00105                 ret = detail::RequiresExplicitCast<value_type>::cast(
    00106                   (1.0 - dy) * a_(i, Diff2D(ix, iy)) +
    00107                   dy * a_(i, Diff2D(ix, iy + 1)));
    00108             }
    00109         }
    00110         else
    00111         {
    00112             if(dy == 0.0)
    00113             {
    00114                 ret = detail::RequiresExplicitCast<value_type>::cast(
    00115                   (1.0 - dx) * a_(i, Diff2D(ix, iy)) +
    00116                   dx * a_(i, Diff2D(ix + 1, iy)));
    00117             }
    00118             else
    00119             {
    00120                 ret = detail::RequiresExplicitCast<value_type>::cast(
    00121                   (1.0 - dx) * (1.0 - dy) * a_(i, Diff2D(ix, iy)) +
    00122                   dx * (1.0 - dy) * a_(i, Diff2D(ix + 1, iy)) +
    00123                   (1.0 - dx) * dy * a_(i, Diff2D(ix, iy + 1)) +
    00124                   dx * dy * a_(i, Diff2D(ix + 1, iy + 1)));
    00125             }
    00126         }
    00127
    00128         return ret;
    00129     }
    00130
    00131     /** Interpolate the data item at a non-integer position.
    00132         This function works as long as 0 <= x < width-1,
    00133         0 <= y < height-1. It is slightly faster than <TT>operator()</TT>.
    00134     */
    00135     template <class ITERATOR>
    00136     value_type unchecked(ITERATOR const & i, float x, float y) const
    00137     {
    00138         int ix = int(x);
    00139         int iy = int(y);
    00140         float dx = x - ix;
    00141         float dy = y - iy;
    00142         return detail::RequiresExplicitCast<value_type>::cast(
    00143                (1.0 - dx) * (1.0 - dy) * a_(i, Diff2D(ix, iy)) +
    00144                dx * (1.0 - dy) * a_(i, Diff2D(ix + 1, iy)) +
    00145                (1.0 - dx) * dy * a_(i, Diff2D(ix, iy + 1)) +
    00146                dx * dy * a_(i, Diff2D(ix + 1, iy + 1)));
    00147     }
    00148
    00149   private:
    00150     ACCESSOR a_;
    00151 };
    00152
    00153 //@}
    00154
    00155 } // namespace vigra
    00156
    00157 #endif /* VIGRA_INTERPOLATING_ACCESSOR_HXX */

© Ullrich Köthe (koethe@informatik.uni-hamburg.de) Cognitive Systems Group, University of Hamburg, Germany | html generated using doxygen and Python VIGRA 1.3.2 (27 Jan 2005)