[GRASS-user] Creating a png file with multiple vector maps

[Anna Petrášová]

Hi,

On Tue, Feb 9, 2021 at 10:25 AM Chris Bartolomei via grass-user <
grass-user at lists.osgeo.org> wrote:

> Good morning :)
> I'm using GRASS 7.4.1 on a Linux cluster so I only have command-line
> capability. I have two vector layers (a country boundary polygon and part
> of an administrative area map - also polygons). I am trying to automate
> creating a PNG file of the admin areas overlaying the country boundary
> therefore all work has to be command-line (in a bash script). I've tried
> this two ways - using the d.mon start=png method and also the ps.map method
> as described below. The d.mon method appears to generate the image with
> only one vector map (not both) and only colors the borders - it won't use
> the fill_color setting. The ps.map method seems to work but assumes the
> image is on a sheet of paper so there's a ton of extra white-space. I'd
> like to use d.mon but I can use ps.map if someone could please let me know
> how to export only the computational region without all the extra 'paper'
> in the image. Here's my code:
>
> g.region vector='Country'
> export GRASS_RENDER_IMMEDIATE=png
> export GRASS_RENDER_WIDTH=640
> export GRASS_RENDER_HEIGHT=480
> export GRASS_RENDER_TRANSPARENT=true
> export GRASS_RENDER_TRUECOLOR=true
> export GRASS_RENDER_FILE=$HOME/country_admin.png
> export GRASS_RENDER_FILE_COMPRESSION=0
> export GRASS_MESSAGE_FORMAT=plain
> d.mon start=png
> d.vect map=Country color=210:210:210 fill_color=153:153:153 display=shape
> type=area
> d.vect map=admin_area color=153:153:153 rgb_column=area_color
> display=shape type=area
> d.mon stop=png
>
> This only produces a png with the last vector listed and only the borders
> are colored with the rgb_column values.
>

I think you are missing  GRASS_RENDER_FILE_READ=TRUE:
https://grass.osgeo.org/grass78/manuals/pngdriver.html

Regarding rgb_column, I am not sure, didn't have time to test.

Anna

>
> If I do this without the d.mon start/stop lines ... i.e. relying on the
> GRASS_RENDER_IMMEDIATE=png only, then only one vector map is converted to
> png however it DOES do the color fill properly. With either above method
> the png is the correct size.
>
> Now using ps.map (same env variable set as above):
>
> g.region vector='Country'
> ps.map input=$HOME/ps_rules.txt out=$HOME/country_admin.ps --overwrite
>   where ps_rules.txt is:
> border y
>   color 81:81:81
>   end
> vareas admin_area
>   layer 1
>   rgbcolumn area_color
>   color 153:153:153
>   end
> vareas Country
>   color 210:210:210
>   fcolor 153:153:153
>   end
>
> We don't have pstopng but we do have ghostscript:
>
> gs-dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -dTextAlphaBits=4
> -dGraphicsAlphaBits=4 -r300 -sOutputFile=$HOME/country_admin.png $HOME/
> country_admin.ps
>
> This creates the correct image (color fills, etc) but has white margins
> and a lot of white space below the image like it is printed at the top of
> a piece of paper.
>
> does anyone have any idea how to create a png with multiple vector maps
> overlaying each other (and not have the extra whitespace too)?
>
> v/r
> Chris
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>
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