Well, it appears that simple direct downloading does not download the real
shapefile. Taking care to actually get a shapefile, the result loads without
problems.
ne_110m_populated_places.shp is a PointShape with 243 shapes (points). If you
display it on a Form (#displayMorphic) you won’t see much (243 hardly visible
dots).
With an application for vector graphics (Roassal?) that can read & display the
vector data we would get much nicer maps...
Hans
From: Baveco, Hans <hans.bav...@wur.nl>
Sent: vrijdag 5 juni 2020 12:44
To: Any question about pharo is welcome <pharo-users@lists.pharo.org>
Subject: [Pharo-users] shape file reading
Hi Hernan
I downloaded this shapefile directly via the browser. Indeed it won’t load, the
type of shape file returned is
self longAt: 33 bigEndian: false -> 577660194
where it should have answered an Integer between 0 and 31
shapeType
"position 32, Integer between 0 and 31, Little Endian"
^shpBytes longAt: 33 bigEndian: false
No idea what could be the cause – apparently the header of the file (the first
100 bytes) is not ok...
Hans
You mean some types are missing? Because I get this error when I try to read
some SHP files: "Types > 20 are not yet accounted for"
I wrote this script to reproduce:
| shpE legend urlRoot urlESRIFilePrefix urlESRIFileShp urlPath response
fileRef |
" Download Shapefile resources "
urlRoot :=
'https://github.com/nvkelso/natural-earth-vector/blob/master/110m_cultural/'.
urlESRIFilePrefix := 'ne_110m_populated_places'.
urlESRIFileShp := urlESRIFilePrefix , '.shp'.
urlPath := urlRoot , urlESRIFilePrefix.
#('.shx' '.dbf' '.shp') do: [ : ext |
| url |
url := (urlPath , ext , '?raw=true') asZnUrl.
(response := ZnEasy get: url) isSuccess
ifFalse: [ self error: 'Cannot download file' ].
fileRef := FileSystem disk workingDirectory / (urlESRIFilePrefix , ext).
fileRef writeStreamDo: [ : stream |
stream nextPutAll: ((ZnByteEncoder newForEncoding: 'koi8r') decodeBytes:
response contents ) ] ].
Once downloaded:
| urlESRIFilePrefix urlESRIFileShp shpE |
urlESRIFilePrefix := 'ne_110m_populated_places'.
urlESRIFileShp := urlESRIFilePrefix , '.shp'.
" Load and display it in Morphic "
shpE := ShapeEnsemble fromFile: urlESRIFileShp.
Maybe it's related with the fact they are encoded as koi8r?
I checked with Zinc downloading first from the browser:
| shpFile |
shpFile := 'ne_110m_admin_0_countries.shp' asFileReference.
[ shpFile binaryReadStreamDo: [ : in |
(ZnCharacterEncoder detectEncoding: in upToEnd) identifier ] ]
on: ZnCharacterEncodingError
do: [ nil ].
Cheers,
Hernán
