00001 #include <grass/gis.h>
00002
00003
00004 #define ZERO(x) x < tolerance && x > -tolerance
00005 #define TOLERANCE 1.0e-10
00006 static double tolerance = TOLERANCE;
00007
00008 int G_set_distance_to_line_tolerance (double t)
00009 {
00010 if (t <= 0.0)
00011 t = TOLERANCE;
00012 tolerance = t;
00013
00014 return 0;
00015 }
00016
00017 double G_distance2_point_to_line (
00018 double x,double y,
00019 double x1,double y1,double x2,double y2)
00020 {
00021 double dx,dy,t;
00022
00023 dx = x2 - x1;
00024 dy = y2 - y1;
00025
00026 if (ZERO(dx) && ZERO(dy))
00027 {
00028 dx = x1 - x;
00029 dy = y1 - y;
00030 return dx*dx + dy*dy;
00031 }
00032
00033 t = (dx * (x - x1) + dy * (y - y1)) / (dx * dx + dy * dy);
00034
00035 if (t < 0.0)
00036 {
00037 dx = x - x1;
00038 dy = y - y1;
00039 }
00040 else if (t > 1.0)
00041 {
00042 dx = x - x2;
00043 dy = y - y2;
00044 }
00045 else
00046 {
00047 dx = x - (dx * t + x1);
00048 dy = y - (dy * t + y1);
00049 }
00050 return dx*dx + dy*dy;
00051 }