Raster to Ascii by python console in QGIS?

Question

I'm working on PyQgis.

I have to convert a raster file to a file .asc. The classic procedure through the Qgis Menu is:

Raster -> Translate (convert format) -> on "Ouput file" select Arc / Info ASCII Grid.

Can this procedure be queried by the python console? What is the command?

EDIT

I tried to run:

processing.runalg('gdalogr:translate', '/path/to/raster.tif',100.0,True,None,0,'',None,False,5,4,75.0,6.0,1.0,False,0,False,None,'/path/to/output.asc')

But the result was:

Error: Wrong parameter value: None

Why?

• Michael Stimson: You can use GDAL_Translate -of AAIGRID from a command window. The raster translate menu is only a shortcut to GDAL_Translate. gdal.org/gdal_translate.html If you only have QGIS installed and not GDAL the paths may not be set correctly, open your command window in the folder that contains the file gdal_translate.exe and it should work; there's no external driver needed for this format so paths shouldn't be an issue.
• Domenico Fuoco: @MichaelStimson sorry but your answer does not help me. I edited my question to make it clearer
• Michael Stimson: It looks like your rtype needs to be specified (last parameter before output file) docs.qgis.org/2.6/en/docs/user_manual/processing_algs/gdalogr/… (default 5 = Float32).

Answer 1

It's probably due to the PROJWIN <ParameterExtent> parameter where you need to specify the extent of the raster layer.

Try running the following:

from PyQt4.QtCore import QFileInfo
import processing
raster = 'path/to/raster'
fileInfo = QFileInfo(raster)
baseName = fileInfo.baseName()
rlayer = QgsRasterLayer(raster, baseName)
extent = rlayer.extent()
xmin, xmax, ymin, ymax = extent.xMinimum(), extent.xMaximum(), extent.yMinimum(), extent.yMaximum()
processing.runalg('gdalogr:translate',rlayer,100.0,True,None,0,'',"%f,%f,%f,%f"% (xmin, xmax, ymin, ymax),False,5,4,75.0,6.0,1.0,False,0,False,None,'/path/to/output.asc')

• Domenico Fuoco: I've already tried this solution and created the file .asc but when I load it on Qgis I get a visual result that is identical, but the maximum and minimum values (in the layer panel legend) are wrong. It is as if the 2 values reported in the legend represent the total number of NODATA and the total number of valid data and not the real value.
• Joseph: @DomenicoFuoco - Right-click your .asc file and to go Properties > Style. In the Load min/max values section, choose the Min / max and set the Accuracy to Actual (slower). Then click Load. This should give you the correct result :)
• Domenico Fuoco: I'm sorry, I had made a mistake in returning your procedure. It works perfectly. Thank you!
• Joseph: @DomenicoFuoco - No problem! Glad you got it working :)