[GRASS-user] Creating a png file with multiple vector maps
Chris Bartolomei
surfcjb at yahoo.com
Tue Feb 16 06:54:29 PST 2021
Mortiz - are those vector layers areas ? I'm guessing the census is an area, the roads are lines and the schools are points, yes? I'm having an issue overlaying two area maps (polygons). i can only get one to show ... I have tried your method with all the export GRASS_RENDER* variables but I have a country polygon map as the bottom later and a selection of a few administrative areas (provinces/states) as the top map and I can only get one or the other to show up. It almost seems as if the transparency doesn't work and what should be transparent in the admin map is actually the background color and blocks the country from being seen.Could you please try your method with a couple area (polygon) vector maps overlaying each other?Thanks!:)
Chris
On Tuesday, February 16, 2021, 4:19:16 AM EST, Moritz Lennert <mlennert at club.worldonline.be> wrote:
Hi Chris,
For me, the following works with the current stable GRASS GIS (7.8.5)
and using maps from the NC demo data set:
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_COMPRESSION=0
export GRASS_MESSAGE_FORMAT=plain
export GRASS_RENDER_FILE_READ=TRUE
g.region vect=census_wake2000
d.vect map=census_wake2000 at PERMANENT fill_color=none
d.vect map=roadsmajor at PERMANENT color=255:0:0:255
d.vect map=schools_wake at PERMANENT fill_color=0:128:0:255
icon=basic/circle size=10
I attach a small thumbnail of the resulting PNG file.
Moritz
On 11/02/21 18:54, Chris Bartolomei via grass-user wrote:
> Good morning Anna,
> It took quite a while of trial and error but I worked out a method that
> kindof works:
> First off - unless someone says otherwise, you can't use the PNG driver
> (d.mon) method to overlay more than one polygon vector. Sorry - it just
> doesn't work. You CAN use the ps.map method - that works really well
> generating the image however it by default assumes you are printing on
> an A4 piece of paper so there's all sorts of white space. The image is
> centered at the top of this fictional piece of paper. In your postscript
> rules file you can use the "maploc" command to position the image
> elsewhere on the page. This is necessary because the next trick changes
> the paper dimensions but it assumes the origin is the lower left corner
> and therefore clips anything that is above the new dimensions. Back to
> postscript commands in the rules file first though ... the ps.map maploc
> command uses inches (why?? it should be points) so an A4 page is 8.27" x
> 11.69" points are 1/72 of an inch thus 595p x 842p - it also has a
> default 36p margin (0.5 inch). You'll need those numbers later. maploc
> also lets you set the size of your image box: maploc {x offset from
> left edge} {y offset from top} {width of box} {height of box} Note: this
> is all done via a BASH script with GRASS 7.4 on Linux (RHEL 7), not
> python. This is my postscript rules file:
>
> maploc 0.1 6.815 6.5 4.875 #468p x 351p map box moved down towards the
> bottom of the page
> # note that if you push it too far down to where the box would run off
> the bottom, the image is
> # resized to fit on the page so do some testing to come up with the
> correct values
> # also I found the computational region controls the aspect ratio so
> although I say
> # 6.5 x 4.875 with the above maploc command, I got a 6.5 x 3.8 inch box.
> border y # add a border to the map frame (box)
> color 81:81:81 # shade of gray
> end # end the border controls
> vareas admin_area # top vector layer to display
> layer 1 # attribute table to use
> rgbcolumn area_color # name of column holding R:G:B values to fill
> the polygons
> color 153:153:153 #boundary color
> end # end the admin_area controls
> vareas Country # this is the bottom vectors to display
> color 210:210:210 #boundary color
> fcolor 153:153:153 #fill color for all polygons
> end # end the Country controls
>
> Here's the command to run to generate the postscript file:
>
> ps.map input=$HOME/ps_rules.txt out=$HOME/color_admin.ps --overwrite
>
> To convert the postscript to PNG I had to use ghostscript - there are
> other tools you can use though.
>
> gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -r300 -dTextAlphaBits=4
> -dGraphicsAlphaBits=4 -dDEVICEWIDTHPOINTS=473 -dDEVICEHEIGHTPOINTS=276
> -dFIXEDMEDIA -dPSFitPage -sOutputFile=$HOME/color_admin.png -c
> "<</PageOffset [-34 78]>> setpagedevice" -f $HOME/color_admin.ps
>
> So the above line needs some explaining
> (http://www.ghostscript.com/doc/9.27/Use.htm) but in a nutshell, the
> parameters to play with are first the Pageoffset [x y] values. They are
> in points not inches ... 1/72 inch = 1 point ... remember the 1/2"
> margins? the -34 gives me 2 points of white space to the left edge of
> the map frame, the 78 I had to play with to push the map frame down to
> the right spot.
> Next is the DEVICEWIDTHPOINTS and DEVICEHEIGHTPOINTS ... again in points
> ... this "trims" the paper to height and width ... set something then
> run it and view the results. Adjust and run again until you get it correct.
>
> It's a royal pain but it seems to work this way. It would sure be nice
> to create a GRASS workspace file and just say "convert this workspace to
> an image" with everything all laid out nicely - like Arc does exporting
> their mxd map files...
>
> I hope this helps someone !
> :)
> Chris
>
>
> On Wednesday, February 10, 2021, 11:08:00 PM EST, Anna Petrášová
> <kratochanna at gmail.com> wrote:
>
>
>
>
> On Tue, Feb 9, 2021 at 4:41 PM Chris Bartolomei <surfcjb at yahoo.com
> <mailto:surfcjb at yahoo.com>> wrote:
>
> Hi Anna - thank you for the suggestion - I tried it but alas, still
> it only outputs a single vector map (layer). I can get either the
> Country vector or the admin_areas vector, but not both overlaid.
> :(
> Chris
>
>
> I realized you are using both environmental variables and d.mon, that
> might cause some issues, you use one or the other. So try to remove the
> lines starting with d.mon.
>
> Hope that helps,
> Anna
>
>
> On Tuesday, February 9, 2021, 1:20:52 PM EST, Anna Petrášová
> <kratochanna at gmail.com <mailto:kratochanna at gmail.com>> wrote:
>
>
> Hi,
>
> On Tue, Feb 9, 2021 at 10:25 AM Chris Bartolomei via grass-user
> <grass-user at lists.osgeo.org <mailto: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
> <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 likeit 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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