[GRASS-dev] [GRASS GIS] #2143: d.legend: add option to output legend definition as text

GDAL · December 13, 2013, 9:45pm

#2143: d.legend: add option to output legend definition as text
-----------------------------------+----------------------------------------
Reporter: wenzeslaus | Owner: grass-dev@…
Type: enhancement | Status: new
Priority: trivial | Milestone: 7.0.0
Component: Display | Version: svn-trunk
Keywords: d.legend, text output | Platform: All
Cpu: All |
-----------------------------------+----------------------------------------
It would be nice if `d.legend` provides a textual output instead of
drawing the legend on the monitor/display. Then the legend definition can
be used to create a GRASS-generated legend in some other context such as
interactive GUI legend or HTML web site.

Output format should be easily parsable. However, I haven't considered all
the possibilities of `d.legend` output. For category maps, it is seems to
be easy, only the category labels can make it harder:

{{{
green forest
blue lakes
black roads
}}}

The gradient legends are bigger problem. The gradient itself might be
simple, e.g. CSS syntax is:
{{{
red 10%, green 90%, blue 95%
}}}
However, how the color breaks are defined and is this compatible between
different environments? And How to define labels which might be placed at
different positions than color breaks?

The output should be file or stdout. I'm not sure about option name; it
should not be confused with output of an image to the file (which is not
possible).

I guess that it is possible to create this functionality using library or
maybe even other modules but `d.legend` already has the functionality to
generate legend and it has the interface to control it with all the fine
tuning.

This ticket is related to #89 which requests the definition as an input
for drawing. Implementing both will cause that `d.legend` looses its core
and becomes just a converter of one legend definition to another. However,
I hope that `d.legend` can handle this loss of identity.

--
Ticket URL: <https://trac.osgeo.org/grass/ticket/2143>
GRASS GIS <http://grass.osgeo.org>

GDAL · February 8, 2014, 2:08am

#2143: d.legend: add option to output legend definition as text
-----------------------------------+----------------------------------------
Reporter: wenzeslaus | Owner: grass-dev@…
Type: enhancement | Status: new
Priority: trivial | Milestone: 7.0.0
Component: Display | Version: svn-trunk
Keywords: d.legend, text output | Platform: All
Cpu: All |
-----------------------------------+----------------------------------------

Comment(by hamish):

Hi,

see r.colors.out (which does most of you are asking for in this ticket I
think) and the approach taken by various grass6 addon modules:
r.colors.out_sld (Mapserver), r.colors.out_vtk (Paraview/VisIt), r.out.gmt
(also creates the GMT color table), and r.out.gdal.

.. or for something local/custom just parse the $MAPSET/colr/ file
directly.

I haven't looked at it in a while, but I imagine the HTML display driver
might have some web-friendly code in it too?

Do you have specific plans on how you'd use the output? or is this more a
general idea?

As the primary author of the current d.legend I'm not exactly enthusiastic
about messing too much with what is already working well. It's a
complicated monolith, and I'd appreciate anyone thinking about changing it
to please contact me first for advice. (or the change will risk be dropped
like the fontscale option soon will be)

I could be sold on renaming it to d.rast.legend, renaming the d.rast.leg
script something else, and coming up with a new separate d.vect.legend
module to make display driver vector legends similar to what ps.map has.
Some parts of the current d.legend could share library functions with
d.vect.legend, but since much of it is just drawing rectangles and much of
the rest is heuristics, I'm not sure how much is actually reusable.

enhancements to d.vect in taking size, rotation, color, etc. from
attribute columns has made much of the thematic legend code redundant
AFAIK, so those can be simplified to a wrapper around d.vect and v.univar.

The 747 cockpit approach of 'd.vect --help' is a big reason why I'd favour
two separate d.rast.legend and d.vect.legend modules instead of combining
two code objects into a common frontend. That distinction would be
invisible to the GUI users and not overwhelming to the command line users.

regards,
Hamish

--
Ticket URL: <http://trac.osgeo.org/grass/ticket/2143#comment:1>
GRASS GIS <http://grass.osgeo.org>

GDAL · February 8, 2014, 2:27am

#2143: d.legend: add option to output legend definition as text
-----------------------------------+----------------------------------------
Reporter: wenzeslaus | Owner: grass-dev@…
Type: enhancement | Status: new
Priority: trivial | Milestone: 7.0.0
Component: Display | Version: svn-trunk
Keywords: d.legend, text output | Platform: All
Cpu: All |
-----------------------------------+----------------------------------------

Comment(by hamish):

ps- since cpt-city (http://soliton.vm.bytemark.co.uk/pub/cpt-city/) was
mentioned, it is worth noting that without clear license we can't
distribute anything from the site directly. But users can use as they see
fit, and there is already grass6 addon in
raster/r.colors.tools/r.cpt2grass for converting CPT color rules into
GRASS color rules format.

wrt to an interval editor (and I freely admit my bias in that IMHO much of
the use of color intervals for continuous-gradient data is statistically
unsound and scientifically counter-productive), for categorical maps
anyway an interactive GUI tool making use of ColorBrewer's color maps
would be a really nice thing (and it is license friendly ta boot). see
mention of it here:
http://grasswiki.osgeo.org/wiki/GRASS_SoC_Ideas_2013#Symbology_.2F_Cartography

--
Ticket URL: <http://trac.osgeo.org/grass/ticket/2143#comment:2>
GRASS GIS <http://grass.osgeo.org>

GDAL · February 8, 2014, 4:40am

#2143: d.legend: add option to output legend definition as text
-----------------------------------+----------------------------------------
Reporter: wenzeslaus | Owner: grass-dev@…
Type: enhancement | Status: new
Priority: trivial | Milestone: 7.0.0
Component: Display | Version: svn-trunk
Keywords: d.legend, text output | Platform: All
Cpu: All |
-----------------------------------+----------------------------------------

Comment(by wenzeslaus):

Replying to [comment:1 hamish]:
>
> see r.colors.out (which does most of you are asking for in this ticket I
think) and the approach taken by various grass6 addon modules:
r.colors.out_sld (Mapserver), r.colors.out_vtk (Paraview/VisIt), r.out.gmt
(also creates the GMT color table), and r.out.gdal.
>
> .. or for something local/custom just parse the $MAPSET/colr/ file
directly.
>
I was not testing these but it seems to me that I would end up in re-
implementing `d.legend`, e.g. when putting there labels or when forcing
other types of legend than the map would use by default.

> I haven't looked at it in a while, but I imagine the HTML display driver
might have some web-friendly code in it too?
>
Last time when I was testing HTML driver I got the impression that it
supports only HTML tag map and that even this is not finished. Probably
the big issue is what HTML driver is supposed to do anyway? Legend
rendered as what in HTML and how this fits together with HTML tag map. But
this is different topic.

> Do you have specific plans on how you'd use the output? or is this more
a general idea?
>
The motivation was the ability to create legend for HTML pages, or
alternatively LaTeX reports. But the idea is general, e.g. font and
generally handling of labels could be important for any output which is
trying to be something more than an raster image.

> As the primary author of the current d.legend I'm not exactly
enthusiastic about messing too much with what is already working well.
It's a complicated monolith, and I'd appreciate anyone thinking about
changing it to please contact me first for advice. (or the change will
risk be dropped like the fontscale option soon will be)
>
Adding there text output is actually trying to avoid the need for bigger
changes in `d.legend` (some super visualizations can be then done
outside).

''The other things are related to wiki:GSoC/2014, so they should be
discussed at mailing list, or the ideas should be updated directly when it
is clear.''

--
Ticket URL: <http://trac.osgeo.org/grass/ticket/2143#comment:3>
GRASS GIS <http://grass.osgeo.org>

GDAL · February 8, 2014, 5:41am

#2143: d.legend: add option to output legend definition as text
-----------------------------------+----------------------------------------
Reporter: wenzeslaus | Owner: grass-dev@…
Type: enhancement | Status: new
Priority: trivial | Milestone: 7.0.0
Component: Display | Version: svn-trunk
Keywords: d.legend, text output | Platform: All
Cpu: All |
-----------------------------------+----------------------------------------

Comment(by hamish):

> I was not testing these but it seems to me that I would end up
> in re-implementing d.legend,

do you mean merging those GMT,Mapserver,VTK output tasks into d.legend?
or rewriting a new d.legend from scratch?

d.legend is for drawing objects on the screen. r.colors.out & friends are
for exporting color tables in ascii or other software's color table
format, r.what.color and 'r.what -r' are two more modules that can help
with that.

the closest a d.* module conceptually comes to providing data output
not display output is d.info or the interactive d.what.* modules.

color table != legend rendering, and color table has its own management
tools already.

> e.g. when putting there labels

? I don't understand, d.legend already supports labels for categorical
legends.

the one thing it doesn't do currently is make adding data units text from
r.support easy (ps.map can do that), so you have to use d.text instead.
the code for that is easy, the hard part (and why I haven't done it yet)
is deciding about the best placement.

> or when forcing other types of legend than the map would use by default.

can you provide an example? I'm not sure what you mean.

The main part of the HTML driver is that it creates a html page with
mouse-over hot-link zones, a less popular web feature now than back in the
90s. I was just wondering aloud if it also had some rrr:ggg:bbb to #aabbcc
conversion code in it, but that's trivial to reimplement so never mind.

> > Do you have specific plans on how you'd use the output? or is this
> > more a general idea?
>
> The motivation was the ability to create legend for HTML pages, or
> alternatively LaTeX reports.

so SVG and PostScript output, not rasterized output? (doing it as a small
PNG file is already possible) Don't the d.* + PNG/Cairo driver and ps.map
+ eps2{foo} already allow this? Some examples would help as I still don't
understand what is wanted.

> But the idea is general, e.g. font and generally handling of labels
> could be important for any output which is trying to be something more
than
> an raster image.

Do you mean arbitrary labels (d.labels and d.text) or the text which is
drawn along with the legend itself? We already have some controls for that
via d.font and enviro variables like GRASS_FONTSIZE and GRASS_FONT. Things
that don't respect those arguably should, and wrapper scripts or custom
GUI menus would allow them to be used from the GUI. What specifically is
missing?

n.b. putting those enviro variables in the library fns is problematic as
you may want to do something complicated with d.text or d.grid using
multiple font sizes or styles within the same module run.

regards,
Hamish

--
Ticket URL: <http://trac.osgeo.org/grass/ticket/2143#comment:4>
GRASS GIS <http://grass.osgeo.org>

GDAL · February 8, 2014, 9:06am

#2143: d.legend: add option to output legend definition as text
-----------------------------------+----------------------------------------
Reporter: wenzeslaus | Owner: grass-dev@…
Type: enhancement | Status: new
Priority: trivial | Milestone: 7.0.0
Component: Display | Version: svn-trunk
Keywords: d.legend, text output | Platform: All
Cpu: All |
-----------------------------------+----------------------------------------

Comment(by neteler):

Replying to [comment:2 hamish]:
> ps- since cpt-city (http://soliton.vm.bytemark.co.uk/pub/cpt-city/) was
> mentioned, it is worth noting that without clear license we can't
> distribute anything from the site directly.

Perhaps take from QGIS then which is GPL 2:

https://github.com/qgis/QGIS/tree/master/resources/cpt-city-qgis-min

--
Ticket URL: <https://trac.osgeo.org/grass/ticket/2143#comment:5>
GRASS GIS <http://grass.osgeo.org>

GDAL · February 9, 2014, 8:01am

#2143: d.legend: add option to output legend definition as text
-----------------------------------+----------------------------------------
Reporter: wenzeslaus | Owner: grass-dev@…
Type: enhancement | Status: new
Priority: trivial | Milestone: 7.0.0
Component: Display | Version: svn-trunk
Keywords: d.legend, text output | Platform: All
Cpu: All |
-----------------------------------+----------------------------------------

Comment(by hamish):

Replying to [comment:5 neteler]:
> Replying to [comment:2 hamish]:
> > ps- since cpt-city (http://soliton.vm.bytemark.co.uk/pub/cpt-city/)
was
> > mentioned, it is worth noting that without clear license we can't
> > distribute anything from the site directly.
>
> Perhaps take from QGIS then which is GPL 2:
>
> https://github.com/qgis/QGIS/tree/master/resources/cpt-city-qgis-min

feel free to audit all the COPYING.xml files within..

for the color tables there which have a GPL2-compatible license and are
nice enough to keep, I suggest to put into addons, see existing ones in:

https://trac.osgeo.org/grass/browser/grass-
addons/grass6/raster/r.colors.tools/palettes/

those are easy to use with 'r.colors rules=', I just keep a symlink to the
checkout'd palettes dir at an easy to reach place.

otherwise, if the license isn't clear or it's just another minor
derivation of "red-blue #17", the user can always use r.cpt2grass
themselves.

Hamish

--
Ticket URL: <https://trac.osgeo.org/grass/ticket/2143#comment:6>
GRASS GIS <http://grass.osgeo.org>

GDAL · May 5, 2014, 10:23am

#2143: d.legend: add option to output legend definition as text
-----------------------------------+----------------------------------------
Reporter: wenzeslaus | Owner: grass-dev@…
Type: enhancement | Status: new
Priority: trivial | Milestone: 7.0.0
Component: Display | Version: svn-trunk
Keywords: d.legend, text output | Platform: All
Cpu: All |
-----------------------------------+----------------------------------------

Comment(by hamish):

the functionality asked for in this wish, as I understand it, seems
already covered by r.colors.out and r.category, amongst others.

ok to close it?

Hamish

--
Ticket URL: <https://trac.osgeo.org/grass/ticket/2143#comment:7>
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