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);
}
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));
}
}
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);
}