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

/*!
  \file lib/gis/window_map.c
  
  \brief GIS Library - Window mapping functions.
  
  (C) 2001-2009, 2011 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 Original author CERL
*/

#include <grass/gis.h>

#include "G.h"

/*!
  \brief Adjust east longitude.
 
  This routine returns an equivalent <i>east</i> that is at least as 
  large as the <i>west</i> coordinate.

  <b>Note:</b> This routine should be used only with
  latitude-longitude coordinates.
 
  \param east east coordinate
  \param west west coordinate
  
  \return east coordinate
*/
double G_adjust_east_longitude(double east, double west)
{
    double shift;

    shift = 0;
    while (east + shift < west)
	shift += 360.0;

    return east + shift;
}

/*!
  \brief Returns east not smaller than west.
  
  If the region projection is <tt>PROJECTION_LL</tt>, then this
  routine returns an equivalent <i>east</i> that is not smaller than 
  the coordinate for the western edge of the region and, if possible, 
  smaller than the coordinate for the eastern edge of the region. 
  Otherwise no adjustment is made and the original <i>east</i> is
  returned.
  
  \param east east coordinate
  \param window pointer to Cell_head
  
  \return east coordinate
*/
double G_adjust_easting(double east, const struct Cell_head *window)
{
    double shift;

    shift = 0;
    if (window->proj == PROJECTION_LL) {
	while (east + shift >= window->east)
	    shift -= 360.0;
	while (east + shift < window->west)
	    shift += 360.0;
    }

    return east + shift;
}

/*!
  \brief Initialize window (region).
*/
void G__init_window(void)
{
    if (G_is_initialized(&G__.window_set))
	return;
    
    G_get_window(&G__.window);

    G_initialize_done(&G__.window_set);
}