gaussian.im

#define IMAGER_NO_CONTEXT
#include "imager.h"
#include <math.h>

static double
gauss(int x, double std) {
  return 1.0/(sqrt(2.0*PI)*std)*exp(-(double)(x)*(double)(x)/(2*std*std));
}

/* Counters are as follows
 l:  lines
 i:  columns
 c:  filter coeffs
 ch: channels
 pc: coeff equalization
*/



int
i_gaussian(i_img *im, double stddev) {
  return i_gaussian2( im, stddev, stddev );
}

typedef struct s_gauss_coeff {
    int diameter;
    int radius;
    double *coeff;
} t_gauss_coeff;

 
static t_gauss_coeff *build_coeff( i_img *im, double stddev ) {
  double *coeff = NULL;
  double pc;
  int radius, diameter, i;
  t_gauss_coeff *ret = mymalloc(sizeof(struct s_gauss_coeff));
  ret->coeff = NULL;

  if (im->bits <= 8)
    radius = ceil(2 * stddev);
  else
    radius = ceil(3 * stddev);

  diameter = 1 + radius * 2;

  coeff = mymalloc(sizeof(double) * diameter);

  for(i=0;i <= radius;i++) 
    coeff[radius + i]=coeff[radius - i]=gauss(i, stddev);
  pc=0.0;
  for(i=0; i < diameter; i++)
    pc+=coeff[i];
  for(i=0;i < diameter;i++) {
    coeff[i] /= pc;
    // im_log((aIMCTX, 1, "i_gaussian2 Y i=%i coeff=%.2f\n", i, coeff[i] ));
  }

  ret->diameter = diameter;
  ret->radius = radius;
  ret->coeff = coeff;
  return ret;
}

static void free_coeff(t_gauss_coeff *co ) {

   if( co->coeff != NULL )
     myfree( co->coeff );
   myfree( co );
}

#define img_copy(dest, src) i_copyto( (dest), (src), 0,0, (src)->xsize,(src)->ysize, 0,0);



int
i_gaussian2(i_img *im, double stddevX, double stddevY) {
  int c, ch;
  i_img_dim x, y;
  double pc;
  t_gauss_coeff *co = NULL;
  double res[MAXCHANNELS];
  i_img *timg;
  i_img *yin;
  i_img *yout;
  dIMCTXim(im);

  im_log((aIMCTX, 1,"i_gaussian2(im %p, stddev %.2f,%.2f)\n",im,stddevX,stddevY));
  i_clear_error();

  if (stddevX < 0) {
    i_push_error(0, "stddevX must be positive");
    return 0;
  }
  if (stddevY < 0) {
    i_push_error(0, "stddevY must be positive");
    return 0;
  }

  if( stddevX == stddevY && stddevY == 0 ) {
    i_push_error(0, "stddevX or stddevY must be positive");
    return 0;
  }


  /* totally silly cutoff */
  if (stddevX > 1000) {
    stddevX = 1000;
  }
  if (stddevY > 1000) {
    stddevY = 1000;
  }

  timg = i_sametype(im, im->xsize, im->ysize);

  if( stddevX > 0 ) {
    /* Build Y coefficient matrix */
    co = build_coeff( im, stddevX );
    im_log((aIMCTX, 1, "i_gaussian2 X coeff radius=%i diamter=%i coeff=%p\n", co->radius, co->diameter, co->coeff));

    /******************/
    /* Process X blur */
    im_log((aIMCTX, 1, "i_gaussian2 X blur from im=%p to timg=%p\n", im, timg));

#code im->bits <= 8
    IM_COLOR rcolor;

    for(y = 0; y < im->ysize; y++) {
      for(x = 0; x < im->xsize; x++) {
        pc=0.0;
        for(ch=0;ch<im->channels;ch++)
          res[ch]=0;
        for(c = 0;c < co->diameter; c++)
          if (IM_GPIX(im,x+c-co->radius,y,&rcolor)!=-1) {
            for(ch=0;ch<im->channels;ch++)
              res[ch]+= rcolor.channel[ch] * co->coeff[c];
            pc+=co->coeff[c];
          }
        for(ch=0;ch<im->channels;ch++) {
          double value = res[ch] / pc;
          rcolor.channel[ch] = value > IM_SAMPLE_MAX ? IM_SAMPLE_MAX : IM_ROUND(value);
        }
        IM_PPIX(timg, x, y, &rcolor);
      }
    }
#/code
    /* processing is im -> timg=yin -> im=yout */
    yin = timg;
    yout = im;
  }
  else {
    im_log((aIMCTX, 1, "i_gaussian2 X coeff is unity\n"));

    /* processing is im=yin -> timg=yout -> im */
    yin = im;
    yout = timg;
  }
  
  if( stddevY > 0 ) {
    if( stddevX != stddevY ) {
      if( co != NULL ) {
        free_coeff(co);
        co = NULL;
      }

      /* Build Y coefficient matrix */
      co = build_coeff( im, stddevY );
      im_log((aIMCTX, 1, "i_gaussian2 Y coeff radius=%i diamter=%i coeff=%p\n", co->radius, co->diameter, co->coeff));
    }

    /******************/
    /* Process Y blur */
    im_log((aIMCTX, 1, "i_gaussian2 Y blur from yin=%p to yout=%p\n", yin, yout));
#code im->bits <= 8
    IM_COLOR rcolor;
    for(x = 0;x < im->xsize; x++) {
      for(y = 0; y < im->ysize; y++) {
        pc=0.0;
        for(ch=0; ch<im->channels; ch++)
          res[ch]=0;
        for(c=0; c < co->diameter; c++)
          if (IM_GPIX(yin, x, y+c-co->radius, &rcolor)!=-1) {
            for(ch=0;ch<yin->channels;ch++) 
              res[ch]+= rcolor.channel[ch] * co->coeff[c];
            pc+=co->coeff[c];
          }
        for(ch=0;ch<yin->channels;ch++) {
          double value = res[ch]/pc;
          rcolor.channel[ch] = value > IM_SAMPLE_MAX ? IM_SAMPLE_MAX : IM_ROUND(value);
        }
        IM_PPIX(yout, x, y, &rcolor);
      }
    }
#/code
    if( im != yout ) {
      im_log((aIMCTX, 1, "i_gaussian2 copying yout=%p to im=%p\n", yout, im));
      img_copy( im, yout );
    }
  }
  else {
    im_log((aIMCTX, 1, "i_gaussian2 Y coeff is unity\n"));
    if( yin == timg ) {
      im_log((aIMCTX, 1, "i_gaussian2 copying timg=%p to im=%p\n", timg, im));
      img_copy( im, timg );
    }
  }

  im_log((aIMCTX, 1, "i_gaussian2 im=%p\n", im));
  im_log((aIMCTX, 1, "i_gaussian2 timg=%p\n", timg));
  im_log((aIMCTX, 1, "i_gaussian2 yin=%p\n", yin));
  im_log((aIMCTX, 1, "i_gaussian2 yout=%p\n", yout));

  if( co != NULL )
    free_coeff(co);

  i_img_destroy(timg);
  
  return 1;
}