Functions

wind_overlap.c File Reference

GIS Library - Window overlap functions. More...

#include <grass/gis.h>
Include dependency graph for wind_overlap.c:

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Functions

int G_window_overlap (const struct Cell_head *window, double N, double S, double E, double W)
 Determins if a box overlays a map window.
double G_window_percentage_overlap (const struct Cell_head *window, double N, double S, double E, double W)
 Determines percentage of box is contained in the window.

Detailed Description

GIS Library - Window overlap functions.

(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:
GRASS GIS Development Team
Date:
1999-2008

Definition in file wind_overlap.c.


Function Documentation

int G_window_overlap ( const struct Cell_head *  window,
double  N,
double  S,
double  E,
double  W 
)

Determins if a box overlays a map window.

Given a map window, and a box of N,S,E,W does the box overlap the map window?

Note: knows about global wrap-around for lat-long.

Parameters:
[in] window pointer to window structure
[in] N north
[in] S south
[in] E east
[in] W west
Returns:
1 if box overlaps window
0 if box does not overlap window

Definition at line 37 of file wind_overlap.c.

double G_window_percentage_overlap ( const struct Cell_head *  window,
double  N,
double  S,
double  E,
double  W 
)

Determines percentage of box is contained in the window.

This version returns the percentage (from 0 to 1) of the box contained in the window. This feature can be used during vector plotting to decide if it is more efficient to do a level-one read of the whole vector map, or to pay the price of a level-two startup so only those arcs that enter the window are actually read.

Parameters:
[in] window pointer to widnow structure
[in] N north
[in] S south
[in] E east
[in] W west
Returns:
percentage of overlap

Definition at line 83 of file wind_overlap.c.