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.
 
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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
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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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 */
 
 
#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 )
{
    short * xdist = (short *)  malloc( width * height * sizeof(short) );
    short * ydist = (short *)  malloc( width * height * sizeof(short) );
    double * gx   = (double *) calloc( width * height, sizeof(double) );
    double * gy      = (double *) calloc( width * height, sizeof(double) );
    double * outside = (double *) calloc( width * height, sizeof(double) );
    double * inside  = (double *) calloc( width * height, sizeof(double) );
    unsigned int i;
 
    // Compute outside = edtaa3(bitmap); % Transform background (0's)
    computegradient( data, width, height, gx, gy);
    edtaa3(data, gx, gy, width, height, xdist, ydist, outside);
    for( i=0; i<width*height; ++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( i=0; i<width*height; ++i)
        data[i] = 1 - data[i];
    computegradient( data, width, height, gx, gy );
    edtaa3( data, gx, gy, width, height, xdist, ydist, inside );
    for( i=0; i<width*height; ++i )
        if( inside[i] < 0 )
            inside[i] = 0.0;
 
    // distmap = outside - inside; % Bipolar distance field
    *vmax = 0.;
    for( i=0; i<width*height; ++i)
    {
        outside[i] -= inside[i];
        if( *vmax < fabs( outside[i] ) )
            *vmax = fabs( outside[i] );
    }
 
    for( i=0; i<width*height; ++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 )
{
    double * data    = (double *) calloc( width * height, sizeof(double) );
    float *out       = (float *) malloc( width * height * sizeof(float) );
    unsigned int i;
 
    // find minimum and maximum values
    double img_min = DBL_MAX;
    double img_max = DBL_MIN;
 
    for( i=0; i<width*height; ++i)
    {
        double v = img[i];
        data[i] = v;
        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( i=0; i<width*height; ++i)
        data[i] = (img[i]-img_min)/img_max;
 
    data = make_distance_mapd(data, width, height, vmax);
 
    // lower to float
    for( i=0; i<width*height; ++i)
        out[i] = (float)(1-data[i]);
 
    free( data );
 
    return out;
}