From: Gavin <gavinpublic@comcast.net>
To: mailing list for ConTeXt users <ntg-context@ntg.nl>,
Hans Hagen <j.hagen@xs4all.nl>
Subject: Re: mp-geo Metapost package with ConTeXt
Date: Fri, 16 Jul 2021 10:20:31 -0600 [thread overview]
Message-ID: <4687ACFD-F694-4FA1-9B18-6A7881705D4B@comcast.net> (raw)
In-Reply-To: <ca1a3fa4-7379-4ca2-e3af-351be783c7cb@xs4all.nl>
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Hi Hans, Aditya, and all,
Me:
>>>> 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/ <https://melusine.eu.org/syracuse/poulecl/mp-geo/>
Aditya:
>> 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.
Hans:
> I was wondering about that too. I admit that I looked into maps years ago but never could find quality data files.
This is great fun! I slightly altered Hans’ code to produce the most basic area preserving projection of North America (code and map below). If anyone else is playing with the mp-geo data, it is in arc minutes, so divide by 60 to get degrees.
For my book I only want 5cm diameter globes with continents, so the map data in the mp-geo package is far more detailed than I need. The code is so fast, the detail doesn’t seem to be a problem.
I just started learning Metapost a month ago, and it’s great. I know almost nothing about Lua, but this looks like a fun project for learning more!
Thanks!
Gavin
P.S. I marked the location of our local ConTeXt users group on the map, in case any of you want to visit.
\starttext
\startluacode
function mp.maptopath(filename)
local t = { cycle = true }
for phi, theta in string.gmatch(io.loaddata(filename),"%(([%+%-%d]+),([%+%-%d]+)%)") do
t[#t+1] = { math.cosd(tonumber(phi)/60)*tonumber(theta+6125)/12, tonumber(phi)/12 }
end
mp.inject.path(t)
end
\stopluacode
\startMPpage
fill lua.mp.maptopath("data/usa1.dat");
fill lua.mp.maptopath("data/usa2.dat") ;
fill lua.mp.maptopath("data/mexique.dat") ;
fill lua.mp.maptopath("data/canada.dat") ;
fill fullcircle scaled 5 shifted (0, 203) withcolor white;
\stopMPpage
\stoptext
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next prev parent reply other threads:[~2021-07-16 16:20 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-14 14:43 Gavin
2021-07-15 15:48 ` Hans Hagen
2021-07-15 16:22 ` Aditya Mahajan
2021-07-15 17:58 ` Hans Hagen
2021-07-15 20:30 ` Bruce Horrocks
2021-07-16 19:55 ` Hans Hagen
2021-07-17 9:53 ` Bruce Horrocks
2021-07-17 10:20 ` Henning Hraban Ramm
2021-07-17 10:45 ` Hans Hagen
2021-07-17 11:05 ` Henning Hraban Ramm
2021-10-22 9:31 ` Henning Hraban Ramm via ntg-context
2021-10-22 13:35 ` Hans Hagen via ntg-context
2021-10-22 14:16 ` Henning Hraban Ramm via ntg-context
2021-10-22 14:27 ` Hans Hagen via ntg-context
2021-07-17 10:53 ` Henning Hraban Ramm
2021-07-17 10:53 ` Hans Hagen
2021-07-17 12:42 ` Arthur Rosendahl
2021-07-17 18:50 ` Hans Hagen
2021-07-18 17:36 ` Henning Hraban Ramm
2021-07-16 16:20 ` Gavin [this message]
[not found] ` <E1B2010C-A435-46AD-BD8E-F4D930827791@me.com>
2021-07-16 19:51 ` Hans Hagen
2021-07-16 20:08 ` Alan Braslau
2021-07-26 21:29 ` Gavin via ntg-context
2021-07-26 23:01 ` Aditya Mahajan via ntg-context
2021-07-27 6:12 ` Gavin via ntg-context
2021-07-27 6:29 ` Alan Braslau via ntg-context
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