wind_overlap.c File Reference

GIS Library - Window overlap functions. More...

#include <grass/gis.h>

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Functions
int	G_window_overlap (const struct Cell_head *window, double N, double S, double E, double W)
	Determines if a box overlays a map window. More...
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. More...

Detailed Description

GIS Library - Window overlap functions.

(C) 2001-2014 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

1999-2014

Definition in file wind_overlap.c.

Function Documentation

G_window_overlap()

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

Determines 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.

G_window_percentage_overlap()

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.