[GRASS-dev] how to derive polygons (bounding boxes) from text strings

[Maris Nartiss]

I did some tinkering around the potential interface for such module:
https://github.com/marisn/grass-addons/tree/v_text_bbox/src/vector/v.text.bbox

Uwe, if nobody else has stepped up to help you, poke me after
Christmas as I might have some spare evening before the New Years eave
to do more fiddling.
Māris.

trešd., 2022. g. 14. dec., plkst. 22:16 — lietotājs Markus Neteler
(<neteler at osgeo.org>) rakstīja:
>
> Hello Uwe,
>
> On Fri, Dec 9, 2022 at 10:29 AM <gisfisch at t-online.de> wrote:
> >
> > Hello list,
> >
> > I have a point feature layer with attributes for a text string (call it 'label') and the fontsize in map units (which are meters in my case).
> >
> > Is there a way in Grass to derive polygons (like boundig boxes) from this input information which enclose the label string letter  when those are used to label the points?
> >
> > For those who know ArcMap: what I mean is exactly what happens when you export Annotation features as Shapes in ArcCatalog: you get a polygon layer in which each text string has a polygon hull which fits the height and width, respectively.
> >
> > From a developer, I heard that this can be done d_get_text_box from display library, which is not exposed to the end user.
>
> Well, it is exposed to the "C language" end user :-)
>
> For a local test, I have added these lines (as a simple debug output):
>
> git diff display/d.text/
> diff --git a/display/d.text/main.c b/display/d.text/main.c
> index a5fb7fec7..0aab3db8d 100644
> --- a/display/d.text/main.c
> +++ b/display/d.text/main.c
> @@ -626,10 +626,12 @@ static void draw_text(char *text, double *x,
> double *y, double size,
>         D_text_rotation(0.0);
>
>      D_get_text_box(text, &t, &b, &l, &r);
> +    fprintf(stdout, "t: %.2f, b: %.2f, l: %.2f, r: %.2f\n", t, b, l, r);
>      t = D_u_to_d_row(t);
>      b = D_u_to_d_row(b);
>      l = D_u_to_d_col(l);
>      r = D_u_to_d_col(r);
> +    fprintf(stdout, "t: %.2f, b: %.2f, l: %.2f, r: %.2f\n", t, b, l, r);
>
>      if (rotation != 0.0)
>         D_text_rotation(rotation * 180.0 / M_PI);
>
>
> I guess it would do what you need - tested in North Carolina sample
> data location:
>
> GRASS nc_spm_08_grass7/user1:d.text >
>
> g.region raster=zipcodes_elev_avg
> d.mon wx0
>
> # test 1: font size 4
> d.text text="This is a test of d.text" color=yellow bgcolor=gray size=4
> t: 228897.44, b: 228500.00, l: 626709.08, r: 634951.64
> t: -26.02, b: 0.00, l: 3.39, r: 543.13
>
> # test 2: font size 6
> d.text text="This is a test of d.text" color=yellow bgcolor=gray size=6
> t: 229096.16, b: 228500.00, l: 626735.00, r: 639098.84
> t: -39.04, b: 0.00, l: 5.09, r: 814.69
>
>
> > Since I am not a programmer, I am looking for help how to use d_get_text_box. My goal ist o integrate it in a
> > simple Python script which I already have. This script can import Shapefiles, do simple GIS processing using
> > GRASS modules and write the shapes back.
>
> The (current) pity is that there is no Python wrapper around the
> display library in
>
> https://github.com/OSGeo/grass/tree/main/python/grass/pygrass
> https://github.com/OSGeo/grass/tree/main/python/grass/script
>
> > Of course, if coding is necessary to accomplish this, I will pay for it.
>
> Maybe not a hard task to write this Python access to the C function
> D_get_text_box() but unfortunately I am lacking time.
> Hopefully someone else here is willing to pick up the task.
>
> Best,
> Markus
>
> > thank you and best regards, Uwe
> >
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