pngdriver(1grass)						Grass User's Manual						 pngdriver(1grass)

NAME

	PNG driver - driver to create PNG and PPM images.
       (drivers)

DESCRIPTION

       The PNG driver generates PNG and PPM images from GRASS display commands.  Per default PNG files are written with this driver. It is started
       as 'pseudo' monitor (image file instead) and when stopped, all output from previously used display commands are written to  the	PNG  image
       file.

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.	If you set GRASS_PNGFILE to a filename which ends in ".ppm", a PPM
	      file will be created (with alpha channel stored in a PGM image, if applicable).  If you set GRASS_PNGFILE to a filename  which  ends
	      in ".bmp", a 32-bpp BMP file will be created (these are not readable by some older viewers).

	      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
	      GRASS_PNG_COMPRESSION=[0|1|9]
	      compression level of PNG files (0 = none, 1 = fastest, 9 = best, default is 6)
	      GRASS_PNG_AUTO_WRITE=[TRUE|FALSE]
	      if  set  to  TRUE,  the image file will be written after each operation (i.e. whenever a client disconnects), rather than only being
	      written out when the driver terminates.
	      GRASS_PNG_READ
	      if TRUE, the PNG driver will initialize the image from the contents of GRASS_PNGFILE.
	      GRASS_PNG_MAPPED
	      if TRUE, the PNG driver will map GRASS_PNGFILE as its framebuffer, rather than using memory. This only works with BMP files.
	      GRASS_RENDER_IMMEDIATE=[TRUE|FALSE]
	      tells the raster library to use its built-in PNG driver rather than connecting to an external  monitor  process  using  sockets.	If
	      TRUE, there is no need to run d.mon start=PNG.

   Example
       Define driver settings (here: bash shell syntax)
       export GRASS_RENDER_IMMEDIATE=TRUE
       export GRASS_TRUECOLOR=TRUE
	Start up the driver
       d.mon start=PNG
	Display raster map and vector polygons
       d.rast somerastermap
       d.vect 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 libpng (see the libpng home page) and zlib (see the zlib home page), all which needs to be installed for the PNG
       driver to work (it's worth it).

       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 environ-
       ment  variables to set the PNG size. If you would like a larger image, multiply both rows and cols by the same whole number to preserve the
       aspect ratio.

       Further PNG file processing (e.g. quantization to 1 bit for monochrome images) can be done with 'pnmquant' of the netpbm tools.

SEE ALSO

	Display drivers
       HTMLMAP driver, PostScript driver, XDRIVER
       d.frame, d.mon, d.rast, d.vect

AUTHOR

       Original version: Per Henrik Johansen  NORGIT AS
       Rewritten by: Glynn Clements, 2003

       Last changed: $Date: 2010-02-18 01:23:37 +0100 (Thu, 18 Feb 2010) $

       Full index

       (C) 2003-2011 GRASS Development Team

GRASS 6.4.2															 pngdriver(1grass)