/usr/include/vigra/project2ellipse.hxx is in libvigraimpex-dev 1.10.0+git20160211.167be93+dfsg-2+b5.
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/* */
/* Copyright 2012 by Frank Lenzen & */
/* Ullrich Koethe */
/* */
/* This file is part of the VIGRA computer vision library. */
/* The VIGRA Website is */
/* http://hci.iwr.uni-heidelberg.de/vigra/ */
/* Please direct questions, bug reports, and contributions to */
/* ullrich.koethe@iwr.uni-heidelberg.de or */
/* vigra@informatik.uni-hamburg.de */
/* */
/* Permission is hereby granted, free of charge, to any person */
/* obtaining a copy of this software and associated documentation */
/* files (the "Software"), to deal in the Software without */
/* restriction, including without limitation the rights to use, */
/* copy, modify, merge, publish, distribute, sublicense, and/or */
/* sell copies of the Software, and to permit persons to whom the */
/* Software is furnished to do so, subject to the following */
/* conditions: */
/* */
/* The above copyright notice and this permission notice shall be */
/* included in all copies or substantial portions of the */
/* Software. */
/* */
/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND */
/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES */
/* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND */
/* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT */
/* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, */
/* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING */
/* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR */
/* OTHER DEALINGS IN THE SOFTWARE. */
/* */
/************************************************************************/
#ifndef VIGRA_PROJECT2ELLIPSE_HXX
#define VIGRA_PROJECT2ELLIPSE_HXX
#include <iostream>
namespace vigra{
namespace detail{
//---------------------------------------------------------------------------
inline void projectEllipse2D_FirstQuad (double &vx, double &vy, double a, double b, const double eps, const int iter_max){
double t=0,tmin,tmax,d1,d2,f,x1,y1,l;
int i;
tmax=std::max(2*a*vx,2*b*vy);
tmin=-b*b;
d1=a*vx/(tmax+a*a);
d2=b*vy/(tmax+b*b);
f=d1*d1+d2*d2-1;
for (i=0;i<iter_max;i++){
t=.5*(tmin+tmax);
d1=a*vx/(t+a*a);
d2=b*vy/(t+b*b);
f=d1*d1+d2*d2-1;
x1=a*vx/(t+a*a);
y1=b*vy/(t+b*b);
l=x1*x1+y1*y1-1;
if (fabs(l)<eps)
break;
if(f>0)
tmin=t;
else if(f<0)
tmax=t;
else
break;
}
d1=vx;
d2=vy;
vx=a*a*vx/(t+a*a);
vy=b*b*vy/(t+b*b);
d1 = vx - d1;
d2 = vy - d2;
return;
}
inline void projectEllipse2D(double &vx, double &vy, const double _a,const double _b,const double eps,const int max_iter){
//double err;
double a=_a,b=_b;
//check if inside ellipse
if (((vx/a)*(vx/a)+(vy/b)*(vy/b))<=1){
return;
}
// special case of a circle
if (fabs(a-b) < eps){
double l = sqrt(vx*vx+vy*vy);
if (l>(a+b)/2.){
vx=(a+b)/(2*l)*vx;
vy=(a+b)/(2*l)*vy;
}
return;
}
// reflect vx -> -vx, if necessary
bool x_reflect;
if (vx > eps){
x_reflect = false;
}
else if (vx < -eps){
x_reflect = true;
vx = -vx;
}
else{
x_reflect = false;
vx = 0.0;
}
// reflect vy -> vy = -V if necessary
bool y_reflect;
if (vy > eps){
y_reflect = false;
}
else if (vy < -eps){
y_reflect = true;
vy = -vy;
}
else{
y_reflect = false;
vy = 0.0;
}
// swap axes if necessary
bool swapped;
if (a >= b){
swapped = false;
}
else{
swapped = true;
std::swap(a,b);
std::swap(vx,vy);
}
if (vx != 0.0){
if (vy != 0.0){
projectEllipse2D_FirstQuad(vx,vy,a,b,eps,max_iter);
}
else{
if (vx < a - b*b/a){
double vx_temp = vx;
vx = a*a*vx/(a*a-b*b);
vy = vy*sqrt(fabs(1.0-vx_temp/a*vx_temp/a));
}
else{
vx = a;
vy = 0.0;
}
}
}
else{
vx = 0.0;
vy = b;
}
if (swapped){
std::swap(vx,vy);
}
if (y_reflect){
vy = -vy;
}
if (x_reflect){
vx = -vx;
}
return;
}
} //closing namespace detail
} //closing namespace vigra
#endif // VIGRA_PROJECT2ELLIPSE_HXX
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