PNG DISPLAY DRIVER
PNG display driver to create PNG, PPM, or BMP images.
The PNG driver generates PNG, PPM, or BMP images from GRASS display
commands. Per default PNG files are written with this driver. This
driver is used by default if
Cairo
driver is not available.
The PNG driver can be enabled by setting
GRASS_RENDER_IMMEDIATE
variable, eg.
export GRASS_RENDER_IMMEDIATE=png
Several environment variables affect the operation of the PNG driver:
- GRASS_RENDER_WIDTH=xxx
the width of the image map (default is 640).
- GRASS_RENDER_HEIGHT=yyy
the height of the image map (default is 480).
- GRASS_RENDER_BACKGROUNDCOLOR=RRGGBB
specifies the background color to use in RGB notation (hex or
R:G:B values). Named colors are also supported. Default
is FFFFFF (white).
- GRASS_RENDER_TRANSPARENT=[TRUE|FALSE]
sets transparent background on (TRUE) or off (FALSE, default).
- GRASS_RENDER_TRUECOLOR=[TRUE|FALSE]
sets true-color support. Default is TRUE.
- GRASS_RENDER_FILE=filename
the filename to put the resulting image in, default is map.png.
If you set GRASS_RENDER_FILE 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_RENDER_FILE to a filename which ends in ".bmp", a 32-bpp
BMP file will be created (these are not readable by some older viewers).
- GRASS_RENDER_FILE_COMPRESSION=[0|1|9]
compression level of PNG files (0 = none, 1 = fastest, 9 = best, default is 6)
- GRASS_RENDER_FILE_READ
if TRUE, the PNG driver will initialize the image from
the contents of GRASS_RENDER_FILE.
- GRASS_RENDER_FILE_MAPPED
if TRUE, the PNG driver
will map GRASS_RENDER_FILE as its framebuffer, rather than using
memory. This only works with BMP files.
export GRASS_RENDER_IMMEDIATE=png
export GRASS_RENDER_TRUECOLOR=TRUE
g.region raster=elevation
d.rast elevation
d.vect roadsmajor color=red
This writes a file named
map.png in your current directory.
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 output images is defined by current region
extents. Use g.region -p to get the number of rows and cols
and use the environment variables to set the image 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.
Cairo driver,
PS driver,
HTML driver,
variables
d.rast,
d.vect,
d.mon,
d.erase,
d.redraw
Original version: Per Henrik Johansen <
phj (at)
norgit.no>
Rewritten by: Glynn Clements, 2003
SOURCE CODE
Available at:
PNG DISPLAY DRIVER source code
(history)
Latest change: Monday Nov 25 21:48:59 2024 in commit: 370a492900ccb7f04ec9e7da9d2766ce1a3d66b6
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© 2003-2024
GRASS Development Team,
GRASS GIS 8.5.0dev Reference Manual