PNG driver

NAME

PNG driver - driver to create PNG images
(drivers)

DESCRIPTION

The PNG driver generates PNG pictures from GRASS display commands.

USAGE

Environment variables

Several environment variables effect the operation of the PNG driver.

GRASS_WIDTH=xxx
the width of the image map (default is 640).
GRASS_HEIGHT=yyy
the height of the image map (default is 480).
GRASS_PNGFILE=filename
the filename to put the resulting image in, default is map.png.
GRASS_BACKGROUNDCOLOR=RRGGBB
specifies the background color to use in RGB notation (hex values). Default is 000000 (black).
GRASS_TRANSPARENT=[TRUE|FALSE]
sets transparent background on (TRUE) or off (FALSE, default).
GRASS_TRUECOLOR=[TRUE|FALSE]
sets true-color support if built with GD-2.0

Example

Start up the driver

         d.mon start=PNG
         d.mon select=PNG

Display raster map and vector polygons

         d.rast somerastermap
         d.vect map=somevectormap color=red

Stop the driver subsequently. This will write a file named map.png to be created in your current directory:
```
         d.mon stop=PNG
```

NOTES

The PNG driver uses the Gd library (http://www.boutell.com/gd/) developed by Boutell.Com, Inc. The Gd library in turn relies on libpng (see the libpng home page) and zlib (see the info-zip home page), all which needs to be installed for the PNG driver to work (it's worth it).

Note that the PNG driver is limited to 8bit colors when compiled against libgd1.x. From libgd2.x onwards true color support is optionally provided.

The resolution of the PNG raster map is defined by the map extents. Use g.region -p to get the number of rows and cols and use the environment variables to set the PNG size.

AUTHOR

Per Henrik Johansen
phj@norgit.no
NORGIT AS

Last changed: $Date: 2002/06/08 14:43:02 $