hello,
When I first loaded a map,I want to display a part of map,I used
Qgsmapcanvas.setextent(),
But the map didn't change. The following code:
QgsMapLayer* Layer = new QgsRasterLayer("Resources/mapdata/zgc.tif",
"gdal", false);
if (!Layer->isValid())
{
//QMessageBox::critical(this, "error", "layer is invalid");
return;
}
QgsMapLayerRegistry::instance()->addMapLayer(Layer);
mapCanvasLayerSet.append(Layer);
mapCanvas->setLayerSet(mapCanvasLayerSet);
mapCanvas->setVisible(true);
QgsCoordinateReferenceSystem wgs84(4326,
QgsCoordinateReferenceSystem::EpsgCrsId);
QgsCoordinateReferenceSystem web(3857,
QgsCoordinateReferenceSystem::EpsgCrsId);
mapCanvas->setDestinationCrs(wgs84);
mapCanvas->setDestinationCrs(web);
mapCanvas->setCrsTransformEnabled(true);
QgsRectangle r(0, 0, 800, 800);
mapCanvas->setExtent(r,true);
mapCanvas->setCachingEnabled(true);
mapCanvas->refresh();
How to use setextent,and how to display a part of map,Can you tell me ?
Thanks for help!!
Li
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