Expanding raster extent with ArcPy?

Question

How can i expand extent of a raster image with Python as the image shown in below. I have the coordinate information of a raster image such as Xmin Ymin Xmax Ymax,how can i expand its extent based on the specified size(Ex, expand 10px or 1px)? I know it can be easily implemented on AML through the command such as setwindow, con(isnull ...etc, but i have no idea on ArcPy.

Does anyone know about it?

Answer 1

Set the Output Extent environment setting with arcpy.env.extent, then make a copy of the raster

import arcpy
from arcpy.sa import *

arcpy.CheckOutExtension('Spatial')

arcpy.env.extent = arcpy.Extent(0,0,10,10)
arcpy.env.cellSize = 1

#Dummy raster just for demonstration
a = CreateConstantRaster(1)
print a.extent.XMin
0.0

#Widen Extent
arcpy.env.extent = arcpy.Extent(-2,-2,12,12)

# Copy the raster
b = a * 1
print b.extent.XMin
-2.0

Raster "b" from above code with NoData symbolized as light blue: