opengrads-devel — OpenGrADS development issues, with focus on interfaces and extensions

Re: [Opengrads-devel] Shapefile extension: first crack

[Arlindo da S. <da...@al...>]

On Nov 26, 2007 1:00 PM, Efren Serra <efr...@me...> wrote:
> Arlindo,
>
> I can help you with 7) below.
>

That would be great. Are you familiar with the Shapefile C library?

                http://shapelib.maptools.org/

Graziano is using it to read shapefiles and I see that t can be used
to create files as well.
My understanding of shapefiles is limited. Skimming through the
documentation I see that it is possible to save polygons to a
shapefile. Is there a way to encode things like:

- color
- transparency
- line thickness

For example, if one saves line segments from a contour plot, each with
different color, some with dashed lines, can they be easily displayed
into GIS software?

Regarding filled polygons, I remember Brian mentioning that shapefiles
have very specific rules about them, and that he would have to rewrite
the shading function to be shapefile compliant.

  Thanks,

         Arlindo



-- 
Arlindo da Silva
da...@al...

[Opengrads-devel] Replacing CVS with git - any thoughts?

[Arlindo da S. <da...@al...>]

All,

  After using CVS for many years I believe is time to move on to a new
source code management system. Of the many limitations that are
driving me nuts are:

1) The inability to work offline (without Internet connection, I mean).
2) The difficulty of branching and most importantly, merging.
3) Need to manage CVS privileges, even for occasional developers (or
else be dealing with patches by e-mail something I don't find very
efficient, specially for large patches).

I always thought the subversion (svn) would be a natural successor of
CVS, "CVS done right" as they say. Until I watched this video by Linus
Torvalds:

   http://video.google.com/videosearch?q=linus+torvals+git&sitesearch=

where he makes the case for "git", a VCS that he wrote originally. I
tend to agree with his main points, specially in which concerns 1) and
2) above. You can get some information on git here:

          http://git.or.cz/

A nice tutorial is here:

         http://www.kernel.org/pub/software/scm/git/docs/tutorial.html

and if you are coming from CVS you may want to read this:

        http://www.kernel.org/pub/software/scm/git/docs/cvs-migration.html

or if you are a svn user

        http://git.or.cz/course/svn.html

   I'd suggest switching the OpenGrADS repository from CVS to "git" on
January 1st.
My idea is to keep a centralized "git" repository on opengrads.org,
perhaps even a git-cvs server if there are people that would prefer a
CVS look-and-feel.

   Does anybody have any thoughts, opinions, concerns, etc, about the subject?

   Thank you,

       Arlindo

-- 
Arlindo da Silva
da...@al...

[Opengrads-devel] Shapefile extension: first crack

[Arlindo da S. <da...@al...>]

Graziano,

   I have an initial implementation of your shapefile "draw polyf"
implemented as a GrADS extension. Just check out the Grads module

% gacvs co Grads
% cd Grads/extensions/shape
% make
% perldoc shape
% setenv GAUDXT ./shape.udxt

For convenience I have incorporated libshp with the sources, at least
for now. Look at file utShape.gs for an example. You will need the
gshhs_land.??? files for running this test, and a GrADS build
supporting UDXTs. You should be able to build the sources you just
checked out.

A few comments:

1) I rearranged your code a bit, grouping together portions that could be reused

2) I added "shp_lines" for my own benefit, it may not be needed in the end as
polyf should handle non-closed polygons as well. At this point,
though, they do not produce the same output.

3) I am not sure whether "shp_polyf" works as you intended. The
polygon fills look funny.

4) The current sources let GrADS handle clipping. Your old function
NormalLon (renamed here StdLon) and the InsideDomain() functions are
effectively disabled. You may have good reasons for re-enabling them.

5) The documentation needs to be filled in.

6) It would be nice to have a nice set of simple examples, with small files.

7) It appears to me that one should be able to write shapefiles with
the contents of
the GrADS "metafile" (with coordinates expressed in lat/lon which I
believed can be accomplished with the appropriate conversion). I went
ahead and put in the skeleton from my "gxyat" extension which grabs
the metafile buffer from memory and translates it. This work would be
better completed by someone with shapefile familiarity. Better yet,
with means of testing it. I have no experience (or personal interest
for that matter) in GIS software, but I realize it would be important
to reach out to the GIS community. Any volunteers to take this on? (I
can help with the metafile translation if needed.)

Efren: have you been able to make progress in this area?

  Please let me know if you have any comments.

     Arlindo

-- 
Arlindo da Silva
da...@al...

[Opengrads-devel] Test, please ignore

[Arlindo da S. <da...@al...>]

xxxx

-- 
Arlindo da Silva
da...@al...