1cairodriver(1)              GRASS GIS User's Manual             cairodriver(1)
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Cairo DISPLAY DRIVER

6       Cairo display driver for bitmap or vector output using the Cairo graph‐
7       ics library.
8

DESCRIPTION

10       The Cairo driver generates PNG, BMP, PPM, PS,  PDF  or  SVG  images  by
11       GRASS  display  commands,  using the Cairo graphics library.  The image
12       format is selected from the extension of the output  file.   The  Cairo
13       driver is used for GRASS display commands by default if available, oth‐
14       erwise PNG driver is used.
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USAGE

17   Environment variables
18       The Cairo driver can be enabled by setting GRASS_RENDER_IMMEDIATE vari‐
19       able, eg.
20       export GRASS_RENDER_IMMEDIATE=cairo
21       Several environment variables affect the operation of the Cairo driver:
22
23           ·   GRASS_RENDER_WIDTH=xxx
24               the width of the image map (default is 640).
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26           ·   GRASS_RENDER_HEIGHT=yyy
27               the height of the image map (default is 480).
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29           ·   GRASS_RENDER_BACKGROUNDCOLOR=RRGGBB
30               specifies  the  background color to use in RGB notation (hex or
31               R:G:B values). Named colors  are  also  supported.  Default  is
32               FFFFFF (white).
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34           ·   GRASS_RENDER_TRANSPARENT=[TRUE|FALSE]
35               sets transparent background on (TRUE) or off (FALSE, default).
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37           ·   GRASS_RENDER_ANTIALIAS
38               can  be  default,  none,  gray,  or  subpixel, corresponding to
39               cairo_antialias_t
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41           ·   GRASS_RENDER_FILE=filename
42               the name and format of the resulting  image  file,  default  is
43               map.png.
44               The image format is determined from the file extension.
45               Supported bitmap formats:
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47               ·   .png - Portable Network Graphics (PNG)
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49               ·   .bmp - Windows Bitmap (BMP, 32-bpp) (these are not readable
50                   by some older viewers)
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52               ·   .ppm - Portable Pixmap (PPM + PGM for alpha channel)
53           Supported vector formats:
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55               ·   .pdf - Portable Document Format (PDF)
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57               ·   .ps - PostScript (PS)
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59               ·   .svg - Scalable Vector Graphics (SVG)
60           (Note: Some formats may not be available, depending on  your  plat‐
61           form and the Cairo library that GRASS was built with.)
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63           ·   GRASS_RENDER_FILE_READ
64               if  TRUE,  the  Cairo driver will initialize the image from the
65               contents of GRASS_RENDER_FILE.
66               (Note: This is only supported for bitmap formats)
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68           ·   GRASS_RENDER_FILE_MAPPED
69               if TRUE, the Cairo driver will  map  GRASS_RENDER_FILE  as  its
70               framebuffer, rather than using memory.
71               (Note: This only works with BMP files.)
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73           ·   GRASS_RENDER_CAIRO_SCREEN
74               defines Cairo screen
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76           ·   GRASS_RENDER_CAIRO_VISUAL
77               defines Cairo visual
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EXAMPLES

80   PNG Example
81       Example: using the driver to generate a PNG file (bash-syntax):
82       export GRASS_RENDER_IMMEDIATE=cairo
83       export GRASS_RENDER_FILE=nc_spm.png
84       export GRASS_RENDER_WIDTH=800
85       export GRASS_RENDER_HEIGHT=800
86       export GRASS_RENDER_FILE_READ=TRUE
87       g.region raster=elevation
88       d.rast map=elevation
89       d.vect map=streams width=1 color=blue fcolor=aqua type=area,line
90       d.vect map=roadsmajor width=2
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92   PDF Examples
93       Example:  using  the driver to generate a PDF vector file with a vector
94       map (bash-syntax):
95       export GRASS_RENDER_IMMEDIATE=cairo
96       export GRASS_RENDER_FILE=nc_spm.pdf
97       export GRASS_RENDER_WIDTH=800
98       export GRASS_RENDER_HEIGHT=800
99       g.region vector=roadsmajor
100       # activate vector font
101       d.font Vera
102       d.vect map=roadsmajor layer=1 display=shape attrcolumn=ROAD_NAME lcolor=0:90:255
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104       Example: using the driver to generate a PDF raster file with  a  raster
105       map (bash-syntax):
106       export GRASS_RENDER_IMMEDIATE=cairo
107       export GRASS_RENDER_FILE=nc_spm.pdf
108       export GRASS_RENDER_WIDTH=800
109       export GRASS_RENDER_HEIGHT=800
110       g.region raster=elevation
111       d.rast map=elevation
112
113   SVG Example
114       Example:  using  the driver to generate a SVG vector file with a vector
115       map (bash-syntax):
116       export GRASS_RENDER_IMMEDIATE=cairo
117       export GRASS_RENDER_FILE=vectormap.svg
118       g.region vector=roadsmajor
119       d.vect map=roadsmajor -c
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NOTES

122       The  driver  is  still  in  development.  Enable   it   by   specifying
123       --with-cairo  when configuring GRASS. This requires a reasonably recent
124       version of the Cairo libraries and a working pkg-config.
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126       Antialiasing is enabled by default for bitmap formats.  There  is  cur‐
127       rently no way of disabling this.
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129       The  resolution  of  the  output  images  is  defined by current region
130       extents. Use g.region -p to get the number of rows and cols and use the
131       environment variables to set the image size. If you would like a larger
132       image, multiply both rows and cols by the same whole number to preserve
133       the aspect ratio.
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135       Cairo supports true vector format output whenever possible. However, if
136       the selected format doesn’t support a necessary feature, Cairo may fall
137       back  on  rendering a bitmap representation of the image wrapped in the
138       selected vector format.
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SEE ALSO

141        PNG driver, PS driver, HTML driver, variables
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143        d.rast, d.vect, d.mon, d.erase, d.redraw
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AUTHOR

146       Lars Ahlzen <lars (at) ahlzen.com>
147       and the GRASS Development Team.
148
149       Main index | Topics index | Keywords index |  Graphical  index  |  Full
150       index
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152       © 2003-2020 GRASS Development Team, GRASS GIS 7.8.5 Reference Manual
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156GRASS 7.8.5                                                     cairodriver(1)
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