On 5 Jun 2020, at 23:19, Hern��n Morales Durand <hernan.morales@gmail.com> wrote:

El vie., 5 jun. 2020 a las 9:27, Baveco, Hans (<hans.baveco@wur.nl>) escribi��:

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).

 

I checked and my previous download method was completely wrong. Now switching from ZnEasy to ZnClient to download and it works nicely:

 | 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' '.cpg' '.prj') do: [ : ext |
  ZnClient new
   url: (urlPath , ext) asZnUrl;
   queryAt: 'raw' put: 'true';
   numberOfRetries: 2;
   enforceHttpSuccess: true;
   downloadTo: urlESRIFilePrefix , ext;
   get ].

" Load and display it in Morphic "
shpE := ShapeEnsemble fromFile: urlESRIFileShp.
" List data fields "
shpE dataFields inspect.
" List all shape records "
shpE shapeRecords inspect.
" Set the current attribute "
shpE attribute: 'NAME'.

legend := ColorLegend mapValuesToRandom: shpE valuesOfCurrentAttribute.
shpE legend: legend.

shpE displayMorphic.

 

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.baveco@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,

 

Hern��n