Geografic-Information-System/lib/vector/Vlib/snap.c

/*!
 * \file snap.c
 *
 * \brief Vector library - Clean vector map (snap lines)
 *
 * Higher level functions for reading/writing/manipulating vectors.
 *
 * (C) 2001-2008 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.
 *
 * \author Radim Blazek
 *
 * \date 2001
 */

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

/* function prototypes */
static int sort_new(const void *pa, const void *pb);

/* Vertex */
typedef struct
{
    double x, y;
    int anchor;			/* 0 - anchor, do not snap this point, that means snap others to this */
    /* >0  - index of anchor to which snap this point */
    /* -1  - init value */
} XPNT;

typedef struct
{
    int anchor;
    double along;
} NEW;

/* This function is called by  RTreeSearch() to add selected node/line/area/isle to thelist */
int add_item(int id, struct ilist *list)
{
    dig_list_add(list, id);
    return 1;
}

/*!
 * \brief Snap selected lines to existing vertex in threshold.
 *
 * Snap selected lines to existing vertices.
 * 
 * \warning Lines are not necessarily snapped to nearest vertex, but to vertex in threshold! 
 *
 * Lines showing how vertices were snapped may be optionally written to error map. 
 * Input map must be opened on level 2 for update at least on GV_BUILD_BASE.
 *
 * \param[in] Map input map where vertices will be snapped
 * \param[in] List_lines list of lines to snap
 * \param[in] thresh threshold in which snap vertices
 * \param[out] Err vector map where lines representing snap are written or NULL
 *
 * \return void
 */

/* As mentioned above, lines are not necessarily snapped to nearest vertex! For example:
   |                    
   | 1         line 3 is snapped to line 1,
   |           then line 2 is not snapped to common node at lines 1 and 3,
   because it is already outside of threshold
   ----------- 3   

   |
   | 2
   |    
 */
void
Vect_snap_lines_list(struct Map_info *Map, struct ilist *List_lines,
		     double thresh, struct Map_info *Err)
{
    struct line_pnts *Points, *NPoints;
    struct line_cats *Cats;
    int line, ltype, line_idx;
    double thresh2;

    struct Node *RTree;
    int point;			/* index in points array */
    int nanchors, ntosnap;	/* number of anchors and number of points to be snapped */
    int nsnapped, ncreated;	/* number of snapped verices, number of new vertices (on segments) */
    int apoints, npoints, nvertices;	/* number of allocated points, registered points, vertices */
    XPNT *XPnts;		/* Array of points */
    NEW *New = NULL;		/* Array of new points */
    int anew = 0, nnew;		/* allocated new points , number of new points */
    struct Rect rect;
    struct ilist *List;
    int *Index = NULL;		/* indexes of anchors for vertices */
    int aindex = 0;		/* allocated Index */

    if (List_lines->n_values < 1)
	return;

    Points = Vect_new_line_struct();
    NPoints = Vect_new_line_struct();
    Cats = Vect_new_cats_struct();
    List = Vect_new_list();
    RTree = RTreeNewIndex();

    thresh2 = thresh * thresh;

    /* Go through all lines in vector, and add each point to structure of points */
    apoints = 0;
    point = 1;			/* index starts from 1 ! */
    nvertices = 0;
    XPnts = NULL;

    for (line_idx = 0; line_idx < List_lines->n_values; line_idx++) {
	int v;

	line = List_lines->value[line_idx];

	G_debug(3, "line =  %d", line);
	if (!Vect_line_alive(Map, line))
	    continue;

	ltype = Vect_read_line(Map, Points, Cats, line);

	for (v = 0; v < Points->n_points; v++) {
	    G_debug(3, "  vertex v = %d", v);
	    nvertices++;

	    /* Box */
	    rect.boundary[0] = Points->x[v];
	    rect.boundary[3] = Points->x[v];
	    rect.boundary[1] = Points->y[v];
	    rect.boundary[4] = Points->y[v];
	    rect.boundary[2] = 0;
	    rect.boundary[5] = 0;

	    /* Already registered ? */
	    Vect_reset_list(List);
	    RTreeSearch(RTree, &rect, (void *)add_item, List);
	    G_debug(3, "List : nvalues =  %d", List->n_values);

	    if (List->n_values == 0) {	/* Not found */
		/* Add to tree and to structure */
		RTreeInsertRect(&rect, point, &RTree, 0);
		if ((point - 1) == apoints) {
		    apoints += 10000;
		    XPnts =
			(XPNT *) G_realloc(XPnts,
					   (apoints + 1) * sizeof(XPNT));
		}
		XPnts[point].x = Points->x[v];
		XPnts[point].y = Points->y[v];
		XPnts[point].anchor = -1;
		point++;
	    }
	}
    }
    npoints = point - 1;

    /* Go through all registered points and if not yet marked mark it as anchor and assign this anchor
     * to all not yet marked points in threshold */
    nanchors = ntosnap = 0;
    for (point = 1; point <= npoints; point++) {
	int i;

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

	if (XPnts[point].anchor >= 0)
	    continue;

	XPnts[point].anchor = 0;	/* make it anchor */
	nanchors++;

	/* Find points in threshold */
	rect.boundary[0] = XPnts[point].x - thresh;
	rect.boundary[3] = XPnts[point].x + thresh;
	rect.boundary[1] = XPnts[point].y - thresh;
	rect.boundary[4] = XPnts[point].y + thresh;
	rect.boundary[2] = 0;
	rect.boundary[5] = 0;

	Vect_reset_list(List);
	RTreeSearch(RTree, &rect, (void *)add_item, List);
	G_debug(4, "  %d points in threshold box", List->n_values);

	for (i = 0; i < List->n_values; i++) {
	    int pointb;
	    double dx, dy, dist2;

	    pointb = List->value[i];
	    if (pointb == point)
		continue;

	    dx = XPnts[pointb].x - XPnts[point].x;
	    dy = XPnts[pointb].y - XPnts[point].y;
	    dist2 = dx * dx + dy * dy;

	    if (dist2 <= thresh2) {
		XPnts[pointb].anchor = point;
		ntosnap++;
	    }
	}
    }

    /* Go through all lines and: 
     *   1) for all vertices: if not anchor snap it to its anchor
     *   2) for all segments: snap it to all anchors in threshold (except anchors of vertices of course) */

    nsnapped = ncreated = 0;

    for (line_idx = 0; line_idx < List_lines->n_values; line_idx++) {
	int v, spoint, anchor;
	int changed = 0;

	line = List_lines->value[line_idx];

	G_debug(3, "line =  %d", line);
	if (!Vect_line_alive(Map, line))
	    continue;

	ltype = Vect_read_line(Map, Points, Cats, line);

	if (Points->n_points >= aindex) {
	    aindex = Points->n_points;
	    Index = (int *)G_realloc(Index, aindex * sizeof(int));
	}

	/* Snap all vertices */
	for (v = 0; v < Points->n_points; v++) {
	    /* Box */
	    rect.boundary[0] = Points->x[v];
	    rect.boundary[3] = Points->x[v];
	    rect.boundary[1] = Points->y[v];
	    rect.boundary[4] = Points->y[v];
	    rect.boundary[2] = 0;
	    rect.boundary[5] = 0;

	    /* Find point ( should always find one point ) */
	    Vect_reset_list(List);

	    RTreeSearch(RTree, &rect, (void *)add_item, List);

	    spoint = List->value[0];
	    anchor = XPnts[spoint].anchor;

	    if (anchor > 0) {	/* to be snapped */
		Points->x[v] = XPnts[anchor].x;
		Points->y[v] = XPnts[anchor].y;
		nsnapped++;
		changed = 1;
		Index[v] = anchor;	/* point on new location */
	    }
	    else {
		Index[v] = spoint;	/* old point */
	    }
	}

	/* New points */
	Vect_reset_line(NPoints);

	/* Snap all segments to anchors in threshold */
	for (v = 0; v < Points->n_points - 1; v++) {
	    int i;
	    double x1, x2, y1, y2, xmin, xmax, ymin, ymax;

	    G_debug(3, "  segment = %d end anchors : %d  %d", v, Index[v],
		    Index[v + 1]);

	    x1 = Points->x[v];
	    x2 = Points->x[v + 1];
	    y1 = Points->y[v];
	    y2 = Points->y[v + 1];

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

	    /* Box */
	    if (x1 <= x2) {
		xmin = x1;
		xmax = x2;
	    }
	    else {
		xmin = x2;
		xmax = x1;
	    }
	    if (y1 <= y2) {
		ymin = y1;
		ymax = y2;
	    }
	    else {
		ymin = y2;
		ymax = y1;
	    }

	    rect.boundary[0] = xmin - thresh;
	    rect.boundary[3] = xmax + thresh;
	    rect.boundary[1] = ymin - thresh;
	    rect.boundary[4] = ymax + thresh;
	    rect.boundary[2] = 0;
	    rect.boundary[5] = 0;

	    /* Find points */
	    Vect_reset_list(List);
	    RTreeSearch(RTree, &rect, (void *)add_item, List);

	    G_debug(3, "  %d points in box", List->n_values);

	    /* Snap to anchor in threshold different from end points */
	    nnew = 0;
	    for (i = 0; i < List->n_values; i++) {
		double dist2, along;

		spoint = List->value[i];
		G_debug(4, "    spoint = %d anchor = %d", spoint,
			XPnts[spoint].anchor);

		if (spoint == Index[v] || spoint == Index[v + 1])
		    continue;	/* end point */
		if (XPnts[spoint].anchor > 0)
		    continue;	/* point is not anchor */

		/* Check the distance */
		dist2 =
		    dig_distance2_point_to_line(XPnts[spoint].x,
						XPnts[spoint].y, 0, x1, y1, 0,
						x2, y2, 0, 0, NULL, NULL,
						NULL, &along, NULL);

		G_debug(4, "      distance = %lf", sqrt(dist2));

		if (dist2 <= thresh2) {
		    G_debug(4, "      anchor in thresh, along = %lf", along);

		    if (nnew == anew) {
			anew += 100;
			New = (NEW *) G_realloc(New, anew * sizeof(NEW));
		    }
		    New[nnew].anchor = spoint;
		    New[nnew].along = along;
		    nnew++;
		}
	    }
	    G_debug(3, "  nnew = %d", nnew);
	    /* insert new vertices */
	    if (nnew > 0) {
		/* sort by distance along the segment */
		qsort(New, sizeof(char) * nnew, sizeof(NEW), sort_new);

		for (i = 0; i < nnew; i++) {
		    anchor = New[i].anchor;
		    /* Vect_line_insert_point ( Points, ++v, XPnts[anchor].x, XPnts[anchor].y, 0); */
		    Vect_append_point(NPoints, XPnts[anchor].x,
				      XPnts[anchor].y, 0);
		    ncreated++;
		}
		changed = 1;
	    }
	}

	/* append end point */
	v = Points->n_points - 1;
	Vect_append_point(NPoints, Points->x[v], Points->y[v], Points->z[v]);

	if (changed) {		/* rewrite the line */
	    Vect_line_prune(NPoints);	/* remove duplicates */
	    if (NPoints->n_points > 1 || ltype & GV_LINES) {
		Vect_rewrite_line(Map, line, ltype, NPoints, Cats);
	    }
	    else {
		Vect_delete_line(Map, line);
	    }
	    if (Err) {
		Vect_write_line(Err, ltype, Points, Cats);
	    }
	}
    }				/* for each line */

    Vect_destroy_line_struct(Points);
    Vect_destroy_line_struct(NPoints);
    Vect_destroy_cats_struct(Cats);
    G_free(XPnts);
    G_free(Index);
    G_free(New);
    RTreeDestroyNode(RTree);
}

/* for qsort */
static int sort_new(const void *pa, const void *pb)
{
    NEW *p1 = (NEW *) pa;
    NEW *p2 = (NEW *) pb;

    if (p1->along < p2->along)
	return -1;
    if (p1->along > p2->along)
	return 1;
    return 1;
}

/*!
 * \brief Snap lines in vector map to existing vertex in threshold.
 *
 * For details see Vect_snap_lines_list()
 *
 * \param[in] Map input map where vertices will be snapped
 * \param[in] type type of lines to snap
 * \param[in] thresh threshold in which snap vertices
 * \param[out] Err vector map where lines representing snap are written or NULL
 *
 * \return void
 */
void
Vect_snap_lines(struct Map_info *Map, int type, double thresh,
		struct Map_info *Err)
{
    int line, nlines, ltype;

    struct ilist *List;

    List = Vect_new_list();

    nlines = Vect_get_num_lines(Map);

    for (line = 1; line <= nlines; line++) {
	G_debug(3, "line =  %d", line);

	if (!Vect_line_alive(Map, line))
	    continue;

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

	if (!(ltype & type))
	    continue;

	Vect_list_append(List, line);
    }

    Vect_snap_lines_list(Map, List, thresh, Err);

    Vect_destroy_list(List);

    return;
}