Well I've managed to find a little time between changing dirty nappies so please find attached my first cut at a patch for shapelib support in plmap I’ve made a few changes to plmap to do this: First is the simple reading of the data from the shapefiles rather than the original files. The .shp and .shx files are needed, none of the other shapefile files are used. The shapelib files can be placed and referenced exactly like the old files, so either in a “special place” (data folder, exe folder, etc) and referenced by filename or anywhere else referenced by full path. Note that the extension can be omitted or included as per the shapelib API. Second is the transformation is now performed after the wraparound fixing. This is because the transformation may be into metres or some other such length unit if a map projection is used (I've just been working with data transformed onto a transverse mercator projection which does exactly this) making wraparound fixing impossible after the transformation has been applied. Third is that wraparound fixing has been rewritten. This was because the previous method broke near the equator, particularly in Africa where there are a number of long straight political boundaries (so point-to-point lon changes can be large and lat can be small). It may be of interest that the new method means that if the user specifies lon on 0-360 scale, but the map is -180-180 (or visa-versa) then the features still plot correctly. From the previous discussions I’m sure there will be a number of avid testers. Example 19 uses plmap, but to run it you will need to get a replacement shapefile map for the globe and usaglobe original maps. For testing I grabbed the 110 m resolution countries map from http://www.naturalearthdata.com/features/and made two copies of the .shp and .shx files, renaming them globe and usaglobe. Putting these in the same location as the usual map files will give you a functioning example 19. If/when people are happy with the patch I'll generate shapefile equivalents of the current maps which will mean that existing code will produce identical output whether or not PLplot has been compiled with shapelib support. The code currently plots polygons and ploylines only, and in both cases plots these as lines with no fill. I had wondered about adding the ability to plot polygons with a fill, but this requires a change or addition to the public API and I'm not sure how useful it would be - It would probably need some way to link different fill syles to different objects within a file and I think we already discussed that this is something it is best to let people code themselves rather than try to turn PLplot into GIS software. Although if people think that it would be useful to have a fill option it's relatively little effort to do - discus!!! Let me know if the patch works for you. Phil
________________________________ From: Alan W. Irwin <ir...@beluga.phys.uvic.ca> To: phil rosenberg <philip_rosenb...@yahoo.com> Cc: "plplot-devel@lists.sourceforge.net" <plplot-devel@lists.sourceforge.net>; Andrew Ross <andrewr...@users.sourceforge.net> Sent: Friday, 5 October 2012, 21:38 Subject: Re: [Plplot-devel] map resolution By the way, I looked for a shapefile viewer on Debian and found thuban. I don't know whether that is the best shapefile viewer for Linux, but it is based on libgda/ogr. When I tried thuban on overall shapefile maps for British Columbian (obtained by following links at http://downloads.cloudmade.com/) it appeared to work instantaneously and well for the size (which totalled 200MB) of the 7 shapefile layers making up the map of British Columbia that is provided by http://downloads.cloudmade.com/. Furthermore, I was much impressed with all the high-resolution local detail (e.g., coastlines, natural features, political boundaries to name three of the most useful shapefile layers available for the British Columbia map) that was available under the thuban zoom mode. By the way, that zoom mode worked essentially instantaneously as well. I assume shapelib will be as fast or faster than libgda/ogr so I think we have a lot to look forward to concerning the speed with which shapelib can deliver shapes behind the scenes to plmap for that function to plot. And to anticipate a possible ( :-) ) further question from Phil, no I don't think we should get into trying to let plmap deal with several shapefile file layers at once. Instead it should be the users' responsibility to specify, e.g., "british_columbia_coastline.shp" as a filename to plmap if they want the B.C. coastlines on their plot, and if a user wants another layer in their plot with natural features on top of those coastlines, they can call plmap again with a different filename for the same region, e.g., "british_columbia_natural.shp". Alan __________________________ Alan W. Irwin Astronomical research affiliation with Department of Physics and Astronomy, University of Victoria (astrowww.phys.uvic.ca). Programming affiliations with the FreeEOS equation-of-state implementation for stellar interiors (freeeos.sf.net); the Time Ephemerides project (timeephem.sf.net); PLplot scientific plotting software package (plplot.sf.net); the libLASi project (unifont.org/lasi); the Loads of Linux Links project (loll.sf.net); and the Linux Brochure Project (lbproject.sf.net). __________________________ Linux-powered Science __________________________
shapelib_v1.patch
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