Example #1
0
float Lowpass::lengthen_quality(
  Streamline *st,
  float radius,
  int nsamples,
  float dist,
  Window2d *win,
  int &which_end
)
{
  int i;
  float rad;
  float delta;
  float x,y;
  float sum1 = 0;
  float sum2 = 0;
  int count1 = 0;
  int count2 = 0;
  VectorField *vf = st->vf;
  //printf("got vector field\n");

  /* kluge to work around problems at the image borders */

  float xmin = 2.0 / xsize;
  float ymin = 2.0 / ysize;
  float xmax = 1 - 2.0 / xsize;
  float ymax = image->getaspect() - 2.0 / ysize;

  /* measure the quality as we move away from the streamline's tail */

  x = st->pts[0].x;
  y = st->pts[0].y;
  rad = radius * rad_image->get_value(x,y) / xsize;
  delta = dist * rad / nsamples;

  for (i = 0; i < nsamples; i++) {

    /* don't go too near the borders */
    if (x < xmin || x > xmax || y < ymin || y > ymax)
      break;

    /* measure the point's quality */
    float value =  image->get_value(x,y);
   // printf("value in intial %f\n",value);
    if (value < target)
      sum1 += Square (target - value);
    count1++;


    /* move further away from the endpoint */
    x -= delta * vf->xval(x,y);
    y -= delta * vf->yval(x,y);
  }

  /* now measure from the head */

  x = st->pts[st->samples - 1].x;
  y = st->pts[st->samples - 1].y;
  rad = radius * rad_image->get_value(x,y) / xsize;
  delta = dist * rad / nsamples;

  for (i = 0; i < nsamples; i++) {

    /* don't go too near the borders */
    if (x < xmin || x > xmax || y < ymin || y > ymax)
      break;

    /* measure the point's quality */
    float value =  image->get_value(x,y);
    if (value < target)
      sum2 += Square (target - value);
    count2++;

    /* move further away from the endpoint */
    x += delta * vf->xval(x,y);
    y += delta * vf->yval(x,y);
  }

  /* determine quality */

  float qual = 0;

  if (count1 + count2 != 0)
    qual = (sum1 + sum2) / (count1 + count2);

  /* say which end needs change more */

  if (count1)
    sum1 /= count1;
  if (count2)
    sum2 /= count2;

  if (sum1 > sum2)
    which_end = TAIL;
  else
    which_end = HEAD;
  //printf("lengthen quality over\n");
  return (qual);
}
Example #2
0
float Lowpass::main_body_quality(
  Streamline *st,
  float radius,
  int nsamples,
  float dist,
  Window2d *win,
  int &which_side
)
{
  int i;
  float rad;
  float delta;
  float x,y;
  float sum = 0;
  int count = 0;
  VectorField *vf = st->vf;

  /* kluge to work around problems at the image borders */

  float xmin = 2.0 / xsize;
  float ymin = 2.0 / ysize;
  float xmax = 1 - 2.0 / xsize;
  float ymax = image->getaspect() - 2.0 / ysize;

  /* measure the quality at several random positions along the streamline */

  for (i = 0; i < nsamples; i++) {

    int index = (int) (st->samples * drand48());
    SamplePoint *sample = &st->pts[index];

    x = sample->x;
    y = sample->y;

    /* don't measure near the borders */
    if (x < xmin || x > xmax || y < ymin || y > ymax)
      continue;

    rad = radius * rad_image->get_value(x,y) / xsize;
    delta = 0.3 * rad / nsamples;

    /* find out how to move perpendicular to the vector field */
    float dx = - delta * vf->yval(x,y);
    float dy =   delta * vf->xval(x,y);

    /* sample along either side of the streamline */
    float x1 = x + dx;
    float y1 = y + dy;
    float x2 = x - dx;
    float y2 = y - dy;

    /* measure the quality at the two points */
    float value1 = image->get_value(x1,y1);
    float value2 = image->get_value(x2,y2);
   // printf("value1: %f, value2: %f\n",value1,value2);

    sum += value1 - value2;

    count++;

  }

  /* return quality */

  if (count == 0)
    return (0.0);
  else {

    if (sum > 0)
      which_side = LEFT;
    else
      which_side = RIGHT;

    return (fabs (sum / count));
  }
}
Example #3
0
float Lowpass::shorten_quality(
  Streamline *st,
  float radius,
  int nsamples,
  float dist,
  Window2d *win,
  int &which_end
)
{
  int i;
  float rad;
  float delta;
  float x,y;
  float sum1 = 0;
  float sum2 = 0;
  int count1 = 0;
  int count2 = 0;
  VectorField *vf = st->vf;

  /* kluge to work around problems at the image borders */

  float xmin = 2.0 / xsize;
  float ymin = 2.0 / ysize;
  float xmax = 1 - 2.0 / xsize;
  float ymax = image->getaspect() - 2.0 / ysize;

  /* measure the quality as we move into the body of the streamline */
  /* from the tail endpoint */

  x = st->pts[0].x;
  y = st->pts[0].y;
  rad = radius * rad_image->get_value(x,y) / xsize;
  delta = dist * rad / nsamples;

  for (i = 0; i < nsamples; i++) {

    /* don't measure near the borders */
    if (x < xmin || x > xmax || y < ymin || y > ymax)
      continue;

    /* measure the point's quality */
    float value =  image->get_value(x,y);
    if (value > target)
      sum1 += Square (target - value);
    count1++;

    /* debug drawing of samples */
    if (win) {
      win->set_color_index (255);
      win->line (x, y, x, y);
    }

    /* move further away from the endpoint */
    x += delta * vf->xval(x,y);
    y += delta * vf->yval(x,y);
  }

  /* now measure from the head */

  x = st->pts[st->samples - 1].x;
  y = st->pts[st->samples - 1].y;
  rad = radius * rad_image->get_value(x,y) / xsize;
  delta = dist * rad / nsamples;

  for (i = 0; i < nsamples; i++) {

    /* don't measure near the borders */
    if (x < xmin || x > xmax || y < ymin || y > ymax)
      continue;

    /* measure the point's quality */
    float value =  image->get_value(x,y);
    if (value > target)
      sum2 += Square (target - value);
    count2++;

    /* debug drawing of samples */
    if (win) {
      win->set_color_index (255);
      win->line (x, y, x, y);
    }

    /* move further away from the endpoint */
    x -= delta * vf->xval(x,y);
    y -= delta * vf->yval(x,y);
  }

  /* determine quality */

  float qual = 0;

  if (count1 + count2 != 0)
    qual = (sum1 + sum2) / (count1 + count2);

  /* say which end needs change more */

  if (count1)
    sum1 /= count1;
  if (count2)
    sum2 /= count2;

  if (sum1 > sum2)
    which_end = TAIL;
  else
    which_end = HEAD;

  return (qual);
}