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

6        PNG driver  - driver to create PNG and PPM images
7       (drivers)
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DESCRIPTION

10       The  PNG  driver  generates  PNG and PPM images from GRASS display com‐
11       mands.  Per default PNG files are written.
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USAGE

14   Environment variables
15       Several environment variables effect the operation of the PNG driver.
16              GRASS_WIDTH=xxx
17              the width of the image map (default is 640).
18              GRASS_HEIGHT=yyy
19              the height of the image map (default is 480).
20              GRASS_PNGFILE=filename
21              the filename to put the resulting image in, default is  map.png.
22              If  you  set GRASS_PNGFILE to a filename which ends in ".ppm", a
23              PPM file will be created.
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25              GRASS_BACKGROUNDCOLOR=RRGGBB
26              specifies the background color to use in RGB notation (hex  val‐
27              ues). Default is 000000 (black).
28              GRASS_TRANSPARENT=[TRUE|FALSE]
29              sets transparent background on (TRUE) or off (FALSE, default).
30              GRASS_TRUECOLOR=[TRUE|FALSE]
31              sets true-color support
32              GRASS_PNG_COMPRESSION=[0|1|9]
33              compression level of PNG files (0 = none, 1 = fastest, 9 = best;
34              default is 6)
35              GRASS_PNG_AUTO_WRITE=[TRUE|FALSE]
36              if set to "TRUE", the image file  will  be  written  after  each
37              operation (i.e. whenever a client disconnects), rather than only
38              being written out when the driver terminates.
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40   Example
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42                d.mon start=PNG
43                d.mon select=PNG
44        Display raster map and vector polygons
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46                d.rast somerastermap
47                d.vect map=somevectormap color=red
48        Stop the driver subsequently. This will write a file named map.png  to
49       be created in your current directory:
50                d.mon stop=PNG
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NOTES

54       The PNG driver uses the libpng (see the libpng home page) and zlib (see
55       the info-zip home page), all which needs to be installed  for  the  PNG
56       driver to work (it's worth it).
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58       The resolution of the PNG raster map is defined by the map extents. Use
59       g.region -p to get the number of rows and cols and use the  environment
60       variables to set the PNG size. If you would like a larger image, multi‐
61       ply both rows and cols by the same whole number to preserve the  aspect
62       ratio.
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64       Further  PNG file processing (e.g. quantization to 1 bit for monochrome
65       images) can be done with 'pnmquant' of the netpbm tools.
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SEE ALSO

68        XDRIVER, d.mon, d.rast, d.vect
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AUTHOR

71       Original version: Per Henrik Johansen
72       phj@norgit.no
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74       NORGIT AS
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76       Rewritten by Glynn Clements, 2003
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78       Last changed: $Date: 2006/09/28 15:27:28 $
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80       Full index
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84GRASS 6.2.2                                                       pngdriver(1)