dangles.c

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#include <stdlib.h>
#include <grass/gis.h>
#include <grass/Vect.h>
#include <grass/glocale.h>

#define REMOVE_DANGLE 0
#define CHTYPE_DANGLE 1
#define SELECT_DANGLE 2

static void dangles(struct Map_info *, int, int, double,
                    struct Map_info *, struct ilist *);

void
Vect_remove_dangles(struct Map_info *Map, int type, double maxlength,
                    struct Map_info *Err)
{
    dangles(Map, type, REMOVE_DANGLE, maxlength, Err, NULL);
}

void
Vect_chtype_dangles(struct Map_info *Map, double maxlength,
                    struct Map_info *Err)
{
    dangles(Map, 0, CHTYPE_DANGLE, maxlength, Err, NULL);
}

void
Vect_select_dangles(struct Map_info *Map, int type, double maxlength,
                    struct ilist *List)
{
    dangles(Map, type, SELECT_DANGLE, maxlength, NULL, List);
}

/*
   Line is considered to be a dangle if on at least one end node is no
   other line of given type(s). If a dangle is formed by more lines,
   such string of lines is taken as one dangle and either deleted are
   all parts or nothing.  Optionally, if chtype is set to 1, only
   GV_BOUNDARY are checked for dangles, and if dangle is found lines
   are not deleted but rewritten with type GVLINE.  Optionally deleted
   dangles are written to error map.  Input map must be opened on level
   2 for update at least on GV_BUILD_BASE.

   Parameters:
   Map input map where have to be deleted
   type type of dangles 
   option dangle option (REMOVE_DANGLE, CHTYPE_DANGLE, SELECT_DANGLE)
   maxlength maxlength of dangles or -1 for all dangles
   Err vector map where deleted dangles are written or NULL
   List_dangle list of feature (selected dangles) ids 
 */
static void dangles(struct Map_info *Map, int type, int option,
                    double maxlength, struct Map_info *Err,
                    struct ilist *List_dangle)
{
    struct line_pnts *Points;
    struct line_cats *Cats;
    int i, line, ltype, next_line = 0, nnodelines;
    int nnodes, node, node1, node2, next_node;
    int lcount, tmp_next_line = 0;
    double length;
    int dangles_removed;        /* number of removed dangles */
    int lines_removed;          /* number of lines removed */
    struct ilist *List;         /* List of lines in chain */
    char *lmsg;

    next_line = tmp_next_line = 0;
    dangles_removed = 0;
    lines_removed = 0;

    type &= GV_LINES;           /* to work only with lines and boundaries */

    if (option == CHTYPE_DANGLE) {
        type = GV_BOUNDARY;     /* process boundaries only */
        lmsg = "changed lines";
    }
    else if (option == REMOVE_DANGLE) {
        lmsg = "removed lines";
    }
    else {
        lmsg = "selected lines";
    }

    if (List_dangle)
        Vect_reset_list(List_dangle);

    Points = Vect_new_line_struct();
    Cats = Vect_new_cats_struct();
    List = Vect_new_list();

    nnodes = Vect_get_num_nodes(Map);
    G_debug(2, "nnodes =  %d", nnodes);

    for (node = 1; node <= nnodes; node++) {
        G_percent(node, nnodes, 1);
        G_debug(3, "node =  %d", node);
        if (!Vect_node_alive(Map, node))
            continue;

        nnodelines = Vect_get_node_n_lines(Map, node);

        lcount = 0;             /* number of lines of given type */
        for (i = 0; i < nnodelines; i++) {
            line = Vect_get_node_line(Map, node, i);
            G_debug(3, "    node line %d = %d", i, line);

            ltype = Vect_read_line(Map, NULL, NULL, abs(line));

            if (ltype & type) {
                lcount++;
                next_line = line;
            }
        }

        Vect_reset_list(List);
        if (lcount == 1) {
            G_debug(3, "    node %d is dangle -> follow the line %d", node,
                    next_line);

            while (next_line != 0) {
                Vect_list_append(List, abs(next_line));

                /* Look at the next end of the line if just one another line of the type is connected */
                Vect_get_line_nodes(Map, abs(next_line), &node1, &node2);
                next_node = next_line > 0 ? node2 : node1;

                G_debug(3, "    next_node = %d", next_node);

                nnodelines = Vect_get_node_n_lines(Map, next_node);

                lcount = 0;     /* number of lines of given type (except current next_line) */
                for (i = 0; i < nnodelines; i++) {
                    line = Vect_get_node_line(Map, next_node, i);
                    G_debug(3, "      node line %d = %d", i, line);

                    ltype = Vect_read_line(Map, NULL, NULL, abs(line));

                    if (ltype & type && abs(line) != abs(next_line)) {
                        lcount++;
                        tmp_next_line = line;
                    }
                }
                if (lcount == 1)
                    next_line = tmp_next_line;
                else
                    next_line = 0;

            }

            /* Length of the chain */
            length = 0;
            for (i = 0; i < List->n_values; i++) {
                G_debug(3, "  chain line %d = %d", i, List->value[i]);
                ltype = Vect_read_line(Map, Points, NULL, List->value[i]);
                length += Vect_line_length(Points);
            }

            if (maxlength < 0 || length < maxlength) {  /* delete the chain */
                G_debug(3, "  delete the chain (length=%g)", length);

                for (i = 0; i < List->n_values; i++) {
                    ltype = Vect_read_line(Map, Points, Cats, List->value[i]);

                    /* Write to Err deleted dangle */
                    if (Err) {
                        Vect_write_line(Err, ltype, Points, Cats);
                    }

                    if (option == REMOVE_DANGLE) {
                        Vect_delete_line(Map, List->value[i]);
                    }
                    else if (option == CHTYPE_DANGLE) {
                        G_debug(3, "  rewrite line %d", List->value[i]);
                        Vect_rewrite_line(Map, List->value[i], GV_LINE,
                                          Points, Cats);
                    }
                    else {
                        if (List_dangle) {
                            Vect_list_append(List_dangle, List->value[i]);
                        }
                    }
                    lines_removed++;
                }
            }                   /* delete the chain */

            dangles_removed++;
        }                       /* lcount == 1 */
    }                           /* node <= nnodes */
}