matplotlib Code

#ifndef lint
static const char SCCSID[]="@(#)PJ_sconics.c	4.1	94/05/22	GIE	REL";
#endif
#define PROJ_PARMS__ \
	double	n; \
	double	rho_c; \
	double	rho_0; \
	double	sig; \
	double	c1, c2; \
	int		type;
#define PJ_LIB__
#include	<projects.h>
#define EULER 0
#define MURD1 1
#define MURD2 2
#define MURD3 3
#define PCONIC 4
#define TISSOT 5
#define VITK1 6
#define EPS10	1.e-10
#define EPS 1e-10
#define LINE2 "\n\tConic, Sph\n\tlat_1= and lat_2="
PROJ_HEAD(tissot, "Tissot")
	LINE2;
PROJ_HEAD(murd1, "Murdoch I")
	LINE2;
PROJ_HEAD(murd2, "Murdoch II")
	LINE2;
PROJ_HEAD(murd3, "Murdoch III")
	LINE2;
PROJ_HEAD(euler, "Euler")
	LINE2;
PROJ_HEAD(pconic, "Perspective Conic")
	LINE2;
PROJ_HEAD(vitk1, "Vitkovsky I")
	LINE2;
/* get common factors for simple conics */
	static int
phi12(PJ *P, double *del) {
	double p1, p2;
	int err = 0;

	if (!pj_param(P->params, "tlat_1").i ||
		!pj_param(P->params, "tlat_2").i) {
		err = -41;
	} else {
		p1 = pj_param(P->params, "rlat_1").f;
		p2 = pj_param(P->params, "rlat_2").f;
		*del = 0.5 * (p2 - p1);
		P->sig = 0.5 * (p2 + p1);
		err = (fabs(*del) < EPS || fabs(P->sig) < EPS) ? -42 : 0;
		*del = *del;
	}
	return err;
}
FORWARD(s_forward); /* spheroid */
	double rho;

	switch (P->type) {
	case MURD2:
		rho = P->rho_c + tan(P->sig - lp.phi);
		break;
	case PCONIC:
		rho = P->c2 * (P->c1 - tan(lp.phi));
		break;
	default:
		rho = P->rho_c - lp.phi;
		break;
	}
	xy.x = rho * sin( lp.lam *= P->n );
	xy.y = P->rho_0 - rho * cos(lp.lam);
	return (xy);
}
INVERSE(s_inverse); /* ellipsoid & spheroid */
	double rho;

	rho = hypot(xy.x, xy.y = P->rho_0 - xy.y);
	if (P->n < 0.) {
		rho = - rho;
		xy.x = - xy.x;
		xy.y = - xy.y;
	}
	lp.lam = atan2(xy.x, xy.y) / P->n;
	switch (P->type) {
	case PCONIC:
		lp.phi = atan(P->c1 - rho / P->c2) + P->sig;
		break;
	case MURD2:
		lp.phi = P->sig - atan(rho - P->rho_c);
		break;
	default:
		lp.phi = P->rho_c - rho;
	}
	return (lp);
}
FREEUP; if (P) pj_dalloc(P); }
	static PJ *
setup(PJ *P) {
	double del, cs;
	int i;

	if( (i = phi12(P, &del)) )
		E_ERROR(i);
	switch (P->type) {
	case TISSOT:
		P->n = sin(P->sig);
		cs = cos(del);
		P->rho_c = P->n / cs + cs / P->n;
		P->rho_0 = sqrt((P->rho_c - 2 * sin(P->phi0))/P->n);
		break;
	case MURD1:
		P->rho_c = sin(del)/(del * tan(P->sig)) + P->sig;
		P->rho_0 = P->rho_c - P->phi0;
		P->n = sin(P->sig);
		break;
	case MURD2:
		P->rho_c = (cs = sqrt(cos(del))) / tan(P->sig);
		P->rho_0 = P->rho_c + tan(P->sig - P->phi0);
		P->n = sin(P->sig) * cs;
		break;
	case MURD3:
		P->rho_c = del / (tan(P->sig) * tan(del)) + P->sig;
		P->rho_0 = P->rho_c - P->phi0;
		P->n = sin(P->sig) * sin(del) * tan(del) / (del * del);
		break;
	case EULER:
		P->n = sin(P->sig) * sin(del) / del;
		del *= 0.5;
		P->rho_c = del / (tan(del) * tan(P->sig)) + P->sig;	
		P->rho_0 = P->rho_c - P->phi0;
		break;
	case PCONIC:
		P->n = sin(P->sig);
		P->c2 = cos(del);
		P->c1 = 1./tan(P->sig);
		if (fabs(del = P->phi0 - P->sig) - EPS10 >= HALFPI)
			E_ERROR(-43);
		P->rho_0 = P->c2 * (P->c1 - tan(del));
		break;
	case VITK1:
		P->n = (cs = tan(del)) * sin(P->sig) / del;
		P->rho_c = del / (cs * tan(P->sig)) + P->sig;
		P->rho_0 = P->rho_c - P->phi0;
		break;
	}
	P->inv = s_inverse;
	P->fwd = s_forward;
	P->es = 0;
	return (P);
}
ENTRY0(euler) P->type = EULER; ENDENTRY(setup(P))
ENTRY0(tissot) P->type = TISSOT; ENDENTRY(setup(P))
ENTRY0(murd1) P->type = MURD1; ENDENTRY(setup(P))
ENTRY0(murd2) P->type = MURD2; ENDENTRY(setup(P))
ENTRY0(murd3) P->type = MURD3; ENDENTRY(setup(P))
ENTRY0(pconic) P->type = PCONIC; ENDENTRY(setup(P))
ENTRY0(vitk1) P->type = VITK1; ENDENTRY(setup(P))