Re: mp-geo Metapost package with ConTeXt

[Hans Hagen <j.hagen@xs4all.nl>]

On 7/15/2021 6:22 PM, Aditya Mahajan wrote:
> On Thu, 15 Jul 2021, Hans Hagen wrote:
> 
>> On 7/14/2021 4:43 PM, Gavin wrote:
>>> Hello ConTeXters,
>>>
>>> I’d like to use the mp-geo Metapost package with ConTeXt to draw simple
>> globes viewed from various directions. The package is here:
>>>
>>> 	https://melusine.eu.org/syracuse/poulecl/mp-geo/
>>>
>>> It looks like the last update was 2008 and I don’t read French, so I though
>> my chances of getting anything to work were pretty small. However, I was
>> pleasantly surprised that this MWE found the mp-geo package, the necessary
>> Metapost files in the ConTeXt installation, and the data files.
>>>
>>> \starttext
>>> \startMPcode
>>> input mp-geo;
>>> figure(-10u,-10u,10u,10u);
>>> Mercator(3,48,30);
>>> fin;
>>> end
>>> \stopMPcode
>>> \stoptext
>>>
>>> While all of the files were found, it did not produce a globe. Instead I got
>> an error complaining about an invalid character in the data files. This error
>> is repeated for about 20 files (a small fraction of the total). I put the
>> first error and its data file below. All the others are identical with
>> different .dat files.
>>>
>>> Maybe it’s just an encoding mismatch or a hidden character I can easily
>> delete or replace. On the other hand, maybe I shouldn't even be attempting
>> this? 2008 is a long time ago in ConTeXt time. Feel free to tell me this
>> project is crazy, but if you have an idea how I can make this work, I’d really
>> appreciate it! It looks like a fun package.
>> Looks interesting (I didn't know about it, also the surface stuff).
>> Anyway, the message relates to scantokens not liking what gets read from
>> a file, quite probably a missing file (I'll make it return a different
>> message but still one needs to be aware of the fact that fiel reading in
>> mp is kind of weird so it really expects a file).
> 
> Actually the data files are fairly simple:
> 
> no_of_points
> <list of coordinates>
> 
> So, it would be much simpler to read and parse it via lua rather than scantokens. Rest of the code simply determines a "view" of what to show. So, it can be a good exercise in lua-MP interface.

I was wondering about that too. I admit that I looked into maps years 
ago but never could find quality data files.

\starttext

\startluacode
     function mp.maptopath(filename)
         local t = { cycle = true }
         for x, y in 
string.gmatch(io.loaddata(filename),"%(([%+%-%d]+),([%+%-%d]+)%)") do
             t[#t+1] = { tonumber(x), tonumber(y) }
         end
         mp.inject.path(t)
     end
\stopluacode

\startMPpage
     draw lua.mp.maptopath("slovenia.dat") ;
\stopMPpage

\startMPpage
     draw lua.mp.maptopath("usa1.dat") rotated 90 ;
\stopMPpage

\startMPpage
     draw lua.mp.maptopath("usa2.dat") ;
\stopMPpage

\stoptext

way to low quality ... we also want multiple shapes i guess .. i wonder 
if someone knows where to get good free data

(projections are more your turf)

Hans


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                                           Hans Hagen | PRAGMA ADE
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