QGIS-2.8-PyQGISDeveloperCookbook-en(12)

为开发人员准备的文档,涵盖QGIS的多种功能实现和代码。

Note:fromQGISversion1.7theproviderstringisstructuredasaURL,sothepathmustbepre xedwith

le://.AlsoitallowsWKT(wellknowntext)formattedgeometriesasanalternativeto“x”and“y” elds,

andallowsthe

coordinatereferencesystemtobespeci ed.Forexample

"shape") GPX les—the“gpx”dataproviderreadstracks,routesandwaypointsfromgpx les.Toopena le,the

type(track/route/waypoint)needstobespeci edaspartoftheurl

SpatiaLitedatabase—supportedfromQGISv1.1.SimilarlytoPostGISdatabases,QgsDataSourceURI

canbeusedforgenerationofdatasourceidenti er

MySQLWKB-basedgeometries,throughOGR—datasourceistheconnectionstringtothetable

WFSconnection:.theconnectionisde nedwithaURIandusingtheWFSprovider

Theuricanbecreatedusingthestandardurllib

library.

3.2RasterLayers

Foraccessingraster les,GDALlibraryisused.Itsupportsawiderangeof leformats.Incaseyouhavetroubles

withopeningsome les,checkwhetheryourGDALhassupportfortheparticularformat(notallformatsare

availablebydefault).Toloadarasterfroma le,specifyits

lenameandbasename