Geografic-Information-System/lib/gis/sample.c

/*!
   \file sample.c

   \brief GIS library - sampling methods (extract a cell value from
   raster map)

   1/2006: moved to libgis from v.sample/v.drape for clone removal

   (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 James Darrell McCauley <darrell mccauley-usa.com>, http://mccauley-usa.com/

   \date 1994
 */

#include <string.h>
#include <unistd.h>
#include <math.h>
#include <grass/gis.h>
#include <grass/glocale.h>

/* prototypes */
static double raster_sample_nearest(int fd,
				    const struct Cell_head *window,
				    struct Categories *cats,
				    double north, double east, int usedesc);
static double raster_sample_bilinear(int fd,
				     const struct Cell_head *window,
				     struct Categories *cats,
				     double north, double east, int usedesc);
static double raster_sample_cubic(int fd,
				  const struct Cell_head *window,
				  struct Categories *cats,
				  double north, double east, int usedesc);
static double scancatlabel(const char *);
static void raster_row_error(const struct Cell_head *window, double north,
			     double east);


/*!
 *  \brief Extract a cell value from raster map.
 *
 *  Extract a cell value from raster map at given northing and easting
 *  with a sampled 3x3 window using a specified interpolation method.
 *
 *  \param fd file descriptor
 *  \param window region settings
 *  \param cats categories
 *  \param north northing position
 *  \param east easting position
 *  \param usedesc flag to scan category label
 *  \param itype interpolation method
 *
 *  \return cell value at given position
 */

double G_get_raster_sample(int fd,
			   const struct Cell_head *window,
			   struct Categories *cats,
			   double north, double east,
			   int usedesc, INTERP_TYPE itype)
{
    double retval;

    switch (itype) {
    case NEAREST:
	retval =
	    raster_sample_nearest(fd, window, cats, north, east, usedesc);
	break;
    case BILINEAR:
	retval =
	    raster_sample_bilinear(fd, window, cats, north, east, usedesc);
	break;
    case CUBIC:
	retval = raster_sample_cubic(fd, window, cats, north, east, usedesc);
	break;
    default:
	G_fatal_error("G_get_raster_sample: %s",
		      _("Unknown interpolation type"));
    }

    return retval;
}


static double raster_sample_nearest(int fd,
				    const struct Cell_head *window,
				    struct Categories *cats,
				    double north, double east, int usedesc)
{
    int row, col;
    double predicted;
    DCELL *maprow = G_allocate_d_raster_buf();

    /* convert northing and easting to row and col, resp */
    row = (int)G_northing_to_row(north, window);
    col = (int)G_easting_to_col(east, window);

    if (G_get_d_raster_row(fd, maprow, row) < 0)
	raster_row_error(window, north, east);

    if (G_is_d_null_value(&(maprow[col]))) {
	predicted = 0.0;
    }
    else if (usedesc) {
	char *buf = G_get_cat(maprow[col], cats);

	G_squeeze(buf);
	predicted = scancatlabel(buf);
    }
    else {
	predicted = maprow[col];
    }

    G_free(maprow);

    return predicted;
}


static double raster_sample_bilinear(int fd,
				     const struct Cell_head *window,
				     struct Categories *cats,
				     double north, double east, int usedesc)
{
    int i, row, col;
    double grid[2][2], tmp1, tmp2;
    DCELL *arow = G_allocate_d_raster_buf();
    DCELL *brow = G_allocate_d_raster_buf();

    /* convert northing and easting to row and col, resp */
    row = (int)G_northing_to_row(north, window);
    col = (int)G_easting_to_col(east, window);

    if (G_get_d_raster_row(fd, arow, row) < 0)
	raster_row_error(window, north, east);

    /*-
     * we need 2x2 pixels to do the interpolation. First we decide if we
     * need the previous or next map row
     */
    if (row == 0) {
	/* arow is at top, must get row below */
	if (G_get_d_raster_row(fd, brow, row + 1) < 0)
	    raster_row_error(window, north, east);
    }
    else if (row + 1 == G_window_rows()) {
	/* amaprow is at bottom, get the one above it */
	/* brow = arow; */
	for (i = 0; i < G_window_cols(); ++i)
	    brow[i] = arow[i];

	row--;

	if (G_get_d_raster_row(fd, arow, row) < 0)
	    raster_row_error(window, north, east);
    }
    else if (north - G_row_to_northing((double)row + 0.5, window) > 0) {
	/* north is above a horizontal centerline going through arow */
	/* brow = arow; */
	for (i = 0; i < G_window_cols(); ++i)
	    brow[i] = arow[i];

	row--;

	if (G_get_d_raster_row(fd, arow, row) < 0)
	    raster_row_error(window, north, east);
    }
    else {
	/* north is below a horizontal centerline going through arow */
	if (G_get_d_raster_row(fd, brow, row + 1) < 0)
	    raster_row_error(window, north, east);
    }

    /*-
     * next, we decide if we need the column to the right or left of the
     * current column using a procedure similar to above
     */
    if (col + 1 == G_window_cols())
	col--;
    else if (east - G_col_to_easting((double)col + 0.5, window) < 0)
	col--;

    /*-
     * now were ready to do bilinear interpolation over
     * arow[col], arow[col+1],
     * brow[col], brow[col+1]
     */

    if (usedesc) {
	char *buf;

	G_squeeze(buf = G_get_cat((int)arow[col], cats));
	grid[0][0] = scancatlabel(buf);
	G_squeeze(buf = G_get_cat((int)arow[col + 1], cats));
	grid[0][1] = scancatlabel(buf);
	G_squeeze(buf = G_get_cat((int)brow[col], cats));
	grid[1][0] = scancatlabel(buf);
	G_squeeze(buf = G_get_cat((int)brow[col + 1], cats));
	grid[1][1] = scancatlabel(buf);
    }
    else {
	grid[0][0] = (double)arow[col];
	grid[0][1] = (double)arow[col + 1];
	grid[1][0] = (double)brow[col];
	grid[1][1] = (double)brow[col + 1];
    }

    /* Treat NULL's as zero */
    if (G_is_d_null_value(&(arow[col])))
	grid[0][0] = 0.0;
    if (G_is_d_null_value(&(arow[col + 1])))
	grid[0][1] = 0.0;
    if (G_is_d_null_value(&(brow[col])))
	grid[1][0] = 0.0;
    if (G_is_d_null_value(&(brow[col + 1])))
	grid[1][1] = 0.0;

    east = fabs(G_col_to_easting((double)col, window) - east);
    while (east > window->ew_res)
	east -= window->ew_res;

    north = fabs(G_row_to_northing((double)row, window) - north);
    while (north > window->ns_res)
	north -= window->ns_res;

    /* we do two linear interpolations along the rows */
    tmp1 = G_interp_linear(east / window->ew_res, grid[0][0], grid[0][1]);
    tmp2 = G_interp_linear(east / window->ew_res, grid[1][0], grid[1][1]);

    G_debug(3, "DIAG: r=%d c=%d t1=%g t2=%g\te=%g n=%g",
	    row, col, tmp1, tmp2, east, north);
    G_debug(3, "DIAG: %g %g\n      %g %g",
	    grid[0][0], grid[0][1], grid[1][0], grid[1][1]);

    /*-
     * Now we interpolate along a line parallel to columns
     * and passing through easting
     */
    G_free(arow);
    G_free(brow);

    return G_interp_linear(north / window->ns_res, tmp1, tmp2);
}


static double raster_sample_cubic(int fd,
				  const struct Cell_head *window,
				  struct Categories *cats,
				  double north, double east, int usedesc)
{
    int i, row, col;
    double grid[4][4], tmp[4];
    DCELL *arow = G_allocate_d_raster_buf();
    DCELL *brow = G_allocate_d_raster_buf();
    DCELL *crow = G_allocate_d_raster_buf();
    DCELL *drow = G_allocate_d_raster_buf();

    /* convert northing and easting to row and col, resp */
    row = G_northing_to_row(north, window);
    col = G_easting_to_col(east, window);

    if (G_get_d_raster_row(fd, arow, row) < 0)
	raster_row_error(window, north, east);

    /* we need 4x4 pixels to do the interpolation. */
    if (row == 0) {
	/* row containing sample is at top, must get three rows below */
	if (G_get_d_raster_row(fd, brow, row + 1) < 0)
	    raster_row_error(window, north, east);
	if (G_get_d_raster_row(fd, crow, row + 2) < 0)
	    raster_row_error(window, north, east);
	if (G_get_d_raster_row(fd, drow, row + 3) < 0)
	    raster_row_error(window, north, east);
    }
    else if (row == 1) {
	/* must get row above and tow rows below */
	for (i = 0; i < G_window_cols(); ++i)
	    brow[i] = arow[i];

	if (G_get_d_raster_row(fd, arow, row - 1) < 0)
	    raster_row_error(window, north, east);
	if (G_get_d_raster_row(fd, crow, row + 1) < 0)
	    raster_row_error(window, north, east);
	if (G_get_d_raster_row(fd, drow, row + 2) < 0)
	    raster_row_error(window, north, east);

	row--;
    }
    else if (row + 1 == G_window_rows()) {
	/* arow is at bottom, get the three above it */
	for (i = 0; i < G_window_cols(); ++i)
	    drow[i] = arow[i];

	if (G_get_d_raster_row(fd, arow, row - 3) < 0)
	    raster_row_error(window, north, east);
	if (G_get_d_raster_row(fd, brow, row - 2) < 0)
	    raster_row_error(window, north, east);
	if (G_get_d_raster_row(fd, crow, row - 1) < 0)
	    raster_row_error(window, north, east);

	row -= 3;
    }
    else if (row + 2 == G_window_rows()) {
	/* arow is next to bottom, get the one below and two above it */
	for (i = 0; i < G_window_cols(); ++i)
	    crow[i] = arow[i];

	if (G_get_d_raster_row(fd, arow, row - 2) < 0)
	    raster_row_error(window, north, east);
	if (G_get_d_raster_row(fd, brow, row - 1) < 0)
	    raster_row_error(window, north, east);
	if (G_get_d_raster_row(fd, drow, row + 1) < 0)
	    raster_row_error(window, north, east);

	row -= 2;
    }
    else if (north - G_row_to_northing((double)row + 0.5, window) > 0) {
	/*
	 * north is above a horizontal centerline going through arow. need two
	 * above and one below
	 */
	for (i = 0; i < G_window_cols(); ++i)
	    crow[i] = arow[i];

	if (G_get_d_raster_row(fd, arow, row - 2) < 0)
	    raster_row_error(window, north, east);
	if (G_get_d_raster_row(fd, brow, row - 1) < 0)
	    raster_row_error(window, north, east);
	if (G_get_d_raster_row(fd, drow, row + 1) < 0)
	    raster_row_error(window, north, east);

	row -= 2;
    }
    else {
	/*
	 * north is below a horizontal centerline going through arow need one
	 * above and two below
	 */
	for (i = 0; i < G_window_cols(); ++i)
	    brow[i] = arow[i];

	if (G_get_d_raster_row(fd, arow, row - 1) < 0)
	    raster_row_error(window, north, east);
	if (G_get_d_raster_row(fd, crow, row + 1) < 0)
	    raster_row_error(window, north, east);
	if (G_get_d_raster_row(fd, drow, row + 2) < 0)
	    raster_row_error(window, north, east);

	row--;
    }

    /*
     * Next, we decide if we need columns to the right and/or left of the
     * current column using a procedure similar to above
     */
    if (col == 0 || col == 1)
	col = 0;
    else if (col + 1 == G_window_cols())
	col -= 3;
    else if (col + 2 == G_window_cols())
	col -= 2;
    else if (east - G_col_to_easting((double)col + 0.5, window) < 0)
	/* east is left of center */
	col -= 2;
    else
	col--;

    /*
     * now were ready to do cubic interpolation over
     * arow[col], arow[col+1], arow[col+2], arow[col+3],
     * brow[col], brow[col+1], brow[col+2], brow[col+3],
     * crow[col], crow[col+1], crow[col+2], crow[col+3],
     * drow[col], drow[col+1], drow[col+2], drow[col+3],
     */

    if (usedesc) {
	char *buf;

	for (i = 0; i < 4; ++i) {
	    G_squeeze(buf = G_get_cat(arow[col + i], cats));
	    grid[0][i] = scancatlabel(buf);
	    G_squeeze(buf = G_get_cat(brow[col + i], cats));
	    grid[1][i] = scancatlabel(buf);
	    G_squeeze(buf = G_get_cat(crow[col + i], cats));
	    grid[2][i] = scancatlabel(buf);
	    G_squeeze(buf = G_get_cat(drow[col + i], cats));
	    grid[3][i] = scancatlabel(buf);
	}
    }
    else {
	for (i = 0; i < 4; ++i) {
	    grid[0][i] = (double)arow[col + i];
	    grid[1][i] = (double)brow[col + i];
	    grid[2][i] = (double)crow[col + i];
	    grid[3][i] = (double)drow[col + i];
	}
    }

    /* Treat NULL cells as 0.0 */
    for (i = 0; i < 4; i++) {
	if (G_is_d_null_value(&(arow[col + i])))
	    grid[0][i] = 0.0;
	if (G_is_d_null_value(&(brow[col + i])))
	    grid[1][i] = 0.0;
	if (G_is_d_null_value(&(crow[col + i])))
	    grid[2][i] = 0.0;
	if (G_is_d_null_value(&(drow[col + i])))
	    grid[3][i] = 0.0;
    }

    /* this needs work here */
    east = fabs(G_col_to_easting((double)col + 1, window) - east);
    while (east > window->ew_res)
	east -= window->ew_res;
    east /= window->ew_res;

    north = fabs(G_row_to_northing((double)row + 1, window) - north);
    while (north > window->ns_res)
	north -= window->ns_res;
    north /= window->ns_res;

    /* we do four cubic convolutions along the rows */
    for (i = 0; i < 4; ++i)
	tmp[i] =
	    G_interp_cubic(east, grid[i][0], grid[i][1], grid[i][2],
			   grid[i][3]);

    G_debug(3,
	    "raster_sample_cubic(): DIAG: (%d,%d) 1=%3.2g 2=%3.2g 3=%3.2g 4=%3.2g\te=%g n=%g",
	    row, col, tmp[0], tmp[1], tmp[2], tmp[3], east, north);

    G_free(arow);
    G_free(brow);
    G_free(crow);
    G_free(drow);

    /* user horner's method again for the final interpolation */
    return G_interp_cubic(north, tmp[0], tmp[1], tmp[2], tmp[3]);
}


static double scancatlabel(const char *str)
{
    double val;

    if (strcmp(str, "no data") != 0)
	sscanf(str, "%lf", &val);
    else {
	G_warning(_("\"no data\" label found; setting to zero"));
	val = 0.0;
    }

    return val;
}


static void raster_row_error(const struct Cell_head *window, double north,
			     double east)
{
    G_debug(3, "DIAG: \tRegion is: n=%g s=%g e=%g w=%g",
	    window->north, window->south, window->east, window->west);
    G_debug(3, "      \tData point is north=%g east=%g", north, east);

    G_fatal_error(_("Problem reading raster map"));
}