How to load a raster layer using PyQGIS? - pyqt4

Question

Although there are some posts on this matter, there is no answer in anyone of them. This is why I am asking it again.
One post I found was https://gis.stackexchange.com/questions/68032/raster-layer-invalid
I read information from the following link: https://hub.qgis.org/wiki/17/Arcgis_rest .
I used the command: gdal_translate "http://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer?f=json&pretty=true" s.xml -of WMS. And it generated the file successfully. However, when I try to open the file and assuming the provider is wms, the code report layer is invalid.
The code I used is:
file = QFileDialog.getOpenFileName(self,
"Open WMS", ".", "WMS (*.xml)")
fileInfo = QFileInfo(file)
# Add the layer
layer = QgsRasterLayer(file, fileInfo.fileName(),"wms")
if not layer.isValid():
print "Failed to load."
return
I just choose the file from the dialog box.
I also tried the other command: qgis.utils.iface.addRasterLayer("http://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer?f=json&pretty=true","raster") by using the following code:
layer = QgsRasterLayer("http://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer?f=json&pretty=true", "layer")
if not layer.isValid():
print "Failed to load."
return
It also report "Failed to load". The original command can be run successfully in QGIS python command line. Also, if I try to enter the code in python console, the layer.isValid() would return true. It is just not working in standalone script.

Answer 1

Answer can be found here: https://gis.stackexchange.com/questions/120823/how-to-load-a-wms-layer-using-pyqgis.
Basically, it is just a version problem. If you have qgis previous than v2.6, it would not work. But it is fixed for 2.6
If it is still not working for you, you most likely have problem for environment variable settings.

Answer 2

This is working for me for single band image.I am using python 2.7 and QGIS 2.0.1 .You can load any raster layer like wms,tiff (single band or multiband) etc. using this.:
def ifile(self):
global fileName
fileName = str(QtGui.QFileDialog.getOpenFileName(self.iface.mainWindow(),"Open Raster File",'C:\\',"raster files(*.tif *.tiff *.TIF *.TIFF *.IMG *.img )"))
if len(fileName) is 0:
return
else:
self.inFileName = fileName;
filelayer = QgsRasterLayer(fileName,os.path.basename(fileName))
if filelayer == None or filelayer.bandCount() != 1:
self.errorMessage = "Not a DEM Image"
QMessageBox.information(self.iface.mainWindow(), "Error", self.errorMessage)
else:
#f=open(str(self.inFileName))
self.dlg.lineEdit.setText(self.inFileName)
if filelayer.isValid():
QgsMapLayerRegistry.instance().addMapLayer(filelayer)
pass