Geografic-Information-System/vector/v.split/main.c

/***************************************************************
 *
 * MODULE:       v.split
 * 
 * AUTHOR(S):    Radim Blazek
 *               
 * PURPOSE:      Split lines to segments
 *               
 * COPYRIGHT:    (C) 2001 by the GRASS Development Team
 *
 *               This program is free software under the 
 *               GNU General Public License (>=v2). 
 *               Read the file COPYING that comes with GRASS
 *               for details.
 *
 **************************************************************/
#include <stdlib.h>
#include <math.h>
#include <grass/gis.h>
#include <grass/Vect.h>
#include <grass/glocale.h>

int main(int argc, char *argv[])
{
    struct GModule *module;
    struct Option *in_opt, *out_opt, *length_opt, *vertices_opt;

    /* struct Option *layer_opt; */
    struct Map_info In, Out;
    struct line_pnts *Points, *Points2;
    struct line_cats *Cats;

    /* int    layer; */
    int line, nlines;
    double length;
    int vertices;

    G_gisinit(argv[0]);

    module = G_define_module();
    module->keywords = _("vector, geometry");
    module->description = "Split lines to shorter segments.";

    in_opt = G_define_standard_option(G_OPT_V_INPUT);
    out_opt = G_define_standard_option(G_OPT_V_OUTPUT);
    /* layer_opt = G_define_standard_option(G_OPT_V_FIELD); */

    length_opt = G_define_option();
    length_opt->key = "length";
    length_opt->type = TYPE_DOUBLE;
    length_opt->required = NO;
    length_opt->multiple = NO;
    length_opt->description = "Maximum segment length.";

    vertices_opt = G_define_option();
    vertices_opt->key = "vertices";
    vertices_opt->type = TYPE_INTEGER;
    vertices_opt->required = NO;
    vertices_opt->multiple = NO;
    vertices_opt->description = "Maximum number of vertices in segment.";

    if (G_parser(argc, argv))
	exit(EXIT_FAILURE);

    /* layer = atoi ( layer_opt->answer ); */

    if ((length_opt->answer && vertices_opt->answer) ||
	!(length_opt->answer || vertices_opt->answer))
	G_fatal_error("Use either length or vertices");

    if (length_opt->answer)
	length = atof(length_opt->answer);

    if (vertices_opt->answer) {
	vertices = atoi(vertices_opt->answer);
	if (vertices < 2)
	    G_fatal_error("Number of vertices must be at least 2");
    }

    Vect_set_open_level(2);
    Vect_open_old(&In, in_opt->answer, "");
    Vect_open_new(&Out, out_opt->answer, 0);
    Vect_copy_head_data(&In, &Out);
    Vect_hist_copy(&In, &Out);
    Vect_hist_command(&Out);

    Points = Vect_new_line_struct();
    Points2 = Vect_new_line_struct();
    Cats = Vect_new_cats_struct();

    nlines = Vect_get_num_lines(&In);

    for (line = 1; line <= nlines; line++) {
	int ltype;

	G_percent(line, nlines, 1);

	ltype = Vect_read_line(&In, Points, Cats, line);

	if (ltype & GV_LINES) {
	    if (length_opt->answer) {
		double l, from, to, step;

		l = Vect_line_length(Points);

		if (l <= length) {
		    Vect_write_line(&Out, ltype, Points, Cats);
		}
		else {
		    int n, i;

		    n = ceil(l / length);
		    step = l / n;
		    from = 0.;

		    for (i = 0; i < n; i++) {
			int ret;
			double x, y;

			if (i == n - 1) {
			    to = l;	/* to be sure that it goes to end */
			}
			else {
			    to = from + step;
			}

			ret = Vect_line_segment(Points, from, to, Points2);
			if (ret == 0) {
			    G_warning
				("Cannot make line segment: %f - %f (line length = %f)",
				 from, to, l);
			    continue;
			}

			/* To be sure that the coordinates are identical */
			if (i > 0) {
			    Points2->x[0] = x;
			    Points2->y[0] = y;
			}
			if (i == n - 1) {
			    Points2->x[Points2->n_points - 1] =
				Points->x[Points->n_points - 1];
			    Points2->y[Points2->n_points - 1] =
				Points->y[Points->n_points - 1];
			}

			Vect_write_line(&Out, ltype, Points2, Cats);

			/* last point */
			x = Points2->x[Points2->n_points - 1];
			y = Points2->y[Points2->n_points - 1];

			from += step;
		    }
		}
	    }
	    else {
		int start = 0;	/* number of coordinates written */

		while (start < Points->n_points - 1) {
		    int i, v;

		    Vect_reset_line(Points2);
		    for (i = 0; i < vertices; i++) {
			v = start + i;
			if (v == Points->n_points)
			    break;

			Vect_append_point(Points2, Points->x[v], Points->y[v],
					  Points->z[v]);
		    }

		    Vect_write_line(&Out, ltype, Points2, Cats);

		    start = v;
		}
	    }
	}
	else {
	    Vect_write_line(&Out, ltype, Points, Cats);
	}
    }

    Vect_close(&In);
    Vect_build(&Out);
    Vect_close(&Out);

    exit(0);
}