Line data    Source code

       1             : /******************************************************************************
       2             :  *
       3             :  * Project:  Marching square algorithm
       4             :  * Purpose:  Core algorithm implementation for contour line generation.
       5             :  * Author:   Oslandia <infos at oslandia dot com>
       6             :  *
       7             :  ******************************************************************************
       8             :  * Copyright (c) 2018, Oslandia <infos at oslandia dot com>
       9             :  *
      10             :  * Permission is hereby granted, free of charge, to any person obtaining a
      11             :  * copy of this software and associated documentation files (the "Software"),
      12             :  * to deal in the Software without restriction, including without limitation
      13             :  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
      14             :  * and/or sell copies of the Software, and to permit persons to whom the
      15             :  * Software is furnished to do so, subject to the following conditions:
      16             :  *
      17             :  * The above copyright notice and this permission notice shall be included
      18             :  * in all copies or substantial portions of the Software.
      19             :  *
      20             :  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
      21             :  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
      22             :  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
      23             :  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
      24             :  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
      25             :  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
      26             :  * DEALINGS IN THE SOFTWARE.
      27             :  ****************************************************************************/
      28             : #ifndef MARCHING_SQUARE_UTILITY_H
      29             : #define MARCHING_SQUARE_UTILITY_H
      30             : 
      31             : #include <limits>
      32             : #include <cmath>
      33             : 
      34             : namespace marching_squares
      35             : {
      36             : 
      37             : // This is used to determine the maximum level value for polygons,
      38             : // the one that spans all the remaining plane
      39             : const double Inf = std::numeric_limits<double>::max();
      40             : 
      41             : const double NaN = std::numeric_limits<double>::quiet_NaN();
      42             : 
      43             : #define debug(format, ...) CPLDebug("MarchingSquare", format, ##__VA_ARGS__)
      44             : 
      45             : // Perturb a value if it is too close to a level value
      46     1707947 : inline double fudge(double level, double value)
      47             : {
      48             :     // FIXME
      49             :     // This is too "hard coded". The perturbation to apply really depend on
      50             :     // values between which we have to interpolate, so that the result of
      51             :     // interpolation should give coordinates that are "numerically" stable for
      52             :     // classical algorithms to work (on polygons for instance).
      53             :     //
      54             :     // Ideally we should probably use snap rounding to ensure no contour lines
      55             :     // are within a user-provided minimum distance.
      56             : 
      57     1707947 :     const double absTol = 1e-6;
      58     1707947 :     return std::abs(level - value) < absTol ? value + absTol : value;
      59             : }
      60             : 
      61             : }  // namespace marching_squares
      62             : #endif