distance_field.c

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/* Freetype GL - A C OpenGL Freetype engine
 *
Copyright 2011-2016 Nicolas P. Rougier
Copyright 2013-2016 Marcel Metz
All rights reserved.
 
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
 
 1. Redistributions of source code must retain the above copyright notice,
    this list of conditions and the following disclaimer.
 
 2. Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.
 
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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 */
 
 
#include <math.h>
#include <float.h>
#include <stdlib.h>
#include <string.h>
#include "edtaa3func.h"
 
   double *
make_distance_mapd( double *data, unsigned int width, unsigned int height, double *vmax )
{
   unsigned int wh = width*height;
   short * xdist = (short *)  malloc( wh * sizeof(short) );
   short * ydist = (short *)  malloc( wh * sizeof(short) );
   double * gx   = (double *) calloc( wh, sizeof(double) );
   double * gy      = (double *) calloc( wh, sizeof(double) );
   double * outside = (double *) calloc( wh, sizeof(double) );
   double * inside  = (double *) calloc( wh, sizeof(double) );
 
   // Compute outside = edtaa3(bitmap); % Transform background (0's)
   computegradient( data, width, height, gx, gy);
   edtaa3(data, gx, gy, width, height, xdist, ydist, outside);
   for (unsigned int i=0; i<wh; i++)
      if( outside[i] < 0.0 )
         outside[i] = 0.0;
 
   // Compute inside = edtaa3(1-bitmap); % Transform foreground (1's)
   memset( gx, 0, sizeof(double)*width*height );
   memset( gy, 0, sizeof(double)*width*height );
   for (unsigned int i=0; i<wh; i++)
      data[i] = 1. - data[i];
   computegradient( data, width, height, gx, gy );
   edtaa3( data, gx, gy, width, height, xdist, ydist, inside );
   for (unsigned int i=0; i<wh; i++)
      if (inside[i] < 0.)
         inside[i] = 0.;
 
   // distmap = outside - inside; % Bipolar distance field
   *vmax = 0.;
   for (unsigned int i=0; i<wh; i++) {
      outside[i] -= inside[i];
      if( *vmax < fabs( outside[i] ) )
         *vmax = fabs( outside[i] );
   }
 
   for (unsigned int i=0; i<wh; i++) {
      double v = outside[i];
      if     ( v < -*vmax) outside[i] = -*vmax;
      else if( v > +*vmax) outside[i] = +*vmax;
      data[i] = (outside[i]+*vmax)/(2. * *vmax);
   }
 
   free( xdist );
   free( ydist );
   free( gx );
   free( gy );
   free( outside );
   free( inside );
   return data;
}
 
float*
make_distance_mapbf( unsigned char *img,
                    unsigned int width, unsigned int height, double *vmax )
{
   unsigned int wh = width * height;
   double * data  = (double *) calloc( wh, sizeof(double) );
   float *out     = (float *) malloc( wh * sizeof(float) );
 
   // find minimum and maximum values
   double img_min = DBL_MAX;
   double img_max = DBL_MIN;
 
   for(unsigned int i=0; i<wh; i++) {
      double v = img[i];
      if (v > img_max)
         img_max = v;
      if (v < img_min)
         img_min = v;
   }
 
   // Map values from 0 - 255 to 0.0 - 1.0
   for (unsigned int i=0; i<wh; i++)
      data[i] = (img[i]-img_min)/img_max;
 
   data = make_distance_mapd( data, width, height, vmax );
 
   // lower to float
   for (unsigned int i=0; i<wh; i++)
      out[i] = (float)(1-data[i]);
 
   free( data );
 
   return out;
}