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

Fri Feb 12 12:00:55 PST 2021

Would this addon be useful? 
https://grass.osgeo.org/grass78/manuals/addons/m.printws.html

On February 11, 2021 6:55:24 PM Chris Bartolomei via grass-user 
<grass-user at lists.osgeo.org> 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> 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> wrote:
>
>
> 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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