tlambert.c - plan9port - [fork] Plan 9 from user space
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       ---
       tlambert.c (926B)
       ---
            1 #include <u.h>
            2 #include <libc.h>
            3 #include "map.h"
            4 
            5 static struct coord stdp0, stdp1;
            6 static double k;
            7 
            8 static int
            9 Xlambert(struct place *place, double *x, double *y)
           10 {
           11         double r;
           12         if(place->nlat.l < -80.*RAD)
           13                 return(-1);
           14         if(place->nlat.l > 89.*RAD)
           15                 r = 0;        /* slovenly */
           16         else
           17                 r = stdp0.c*exp(0.5*k*log(
           18                    (1+stdp0.s)*(1-place->nlat.s)/((1-stdp0.s)*(1+place->nlat.s))));
           19         if(stdp1.l<0.)
           20                 r = -r;
           21         *x = - r*sin(k * place->wlon.l);
           22         *y = - r*cos(k * place->wlon.l);
           23         return(1);
           24 }
           25 
           26 proj
           27 lambert(double par0, double par1)
           28 {
           29         double temp;
           30         if(fabs(par0)>fabs(par1)){
           31                 temp = par0;
           32                 par0 = par1;
           33                 par1 = temp;
           34         }
           35         deg2rad(par0, &stdp0);
           36         deg2rad(par1, &stdp1);
           37         if(fabs(par1+par0)<.1)
           38                 return(mercator());
           39         if(fabs(par1-par0)<.1)
           40                 return(perspective(-1.));
           41         if(fabs(par0)>89.5||fabs(par1)>89.5)
           42                 return(0);
           43         k = 2*log(stdp1.c/stdp0.c)/log(
           44                 (1+stdp0.s)*(1-stdp1.s)/((1-stdp0.s)*(1+stdp1.s)));
           45         return(Xlambert);
           46 }