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I would like to reclass raster image with PyQGIS command from the Python Console. It runs without error but nothing is created. I have tried a lot of codes from here, but nothing is working.

from PyQt4.QtCore import QFileInfo 
import processing

# Define input and output paths
filePath = "/home/lukas/Desktop/Sentinel/flood.tif"
output = "/home/lukas/Desktop/Sentinel/flood_reclass.tif"
rules = "/home/lukas/Desktop/pyqgis/reclass.txt"

# Get raster data
fileInfo = QFileInfo(filePath)
baseName = fileInfo.baseName()
rlayer = QgsRasterLayer(filePath, baseName)

# Define the minimum extent of the region
extent = rlayer.extent()
xmin = extent.xMinimum()
xmax = extent.xMaximum()
ymin = extent.yMinimum()
ymax = extent.yMaximum()

import processing
processing.runalg("grass7:r.reclass", rlayer,None, rules, 
"%f,%f,%f,%f"% (xmin, xmax, ymin, ymax), 0.0, output)

Console show no error but there is no result. I have tried to run this in tool, with these layers and rules file and it was working. When I copy command from processing tools history - which worked in tool - it is not working in console.

5

There are some syntax errors.

If you run this code from the Python Console:

import processing
processing.alghelp("grass7:r.reclass")

you will get:

ALGORITHM: r.reclass - Creates a new map layer whose category values are based upon a reclassification of the categories in an existing raster map layer.
    input <ParameterRaster>
    rules <ParameterFile>
    txtrules <ParameterString>
    GRASS_REGION_PARAMETER <ParameterExtent>
    GRASS_REGION_CELLSIZE_PARAMETER <ParameterNumber>
    output <OutputRaster>

This means that you need to define the rules before the txtrules (this is the first syntax error).

Finally, since you have already defined a reclassification file with rules, try to replace None with "".

The following code should work (it worked for me):

from PyQt4.QtCore import QFileInfo 
import processing

# Define input and output paths
filePath = "/home/lukas/Desktop/Sentinel/flood.tif"
output = "/home/lukas/Desktop/Sentinel/flood_reclass.tif"
rules = "/home/lukas/Desktop/pyqgis/reclass.txt"

# Get raster data
fileInfo = QFileInfo(filePath)
baseName = fileInfo.baseName()
rlayer = QgsRasterLayer(filePath, baseName)

# Define the minimum extent of the region
extent = rlayer.extent()
xmin = extent.xMinimum()
xmax = extent.xMaximum()
ymin = extent.yMinimum()
ymax = extent.yMaximum()

import processing
processing.runalg("grass7:r.reclass", rlayer,rules, "", 
"%f,%f,%f,%f"% (xmin, xmax, ymin, ymax), 0.0, output)
  • 1
    Thank you very much mgri :) You have solved my problem ! :) – zubro Aug 30 '17 at 11:48

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