When I use 'Plus' in Spatial Analyst to add together two 8-bit unsigned rasters (pixel values 0-100) the output raster is 8-bit unsigned (pixel values 0-200) but when I try and do the same thing running a python script the output is a 32 signed raster (pixel values 0-200) . How can I adjust my code to have the output be an 8-bit raster?

# Import needed modules
import arcpy
from arcpy.sa import *
raster1 = arcpy.Raster("C:\Users\XXX\Desktop\Raster_test\Confidence_2008_56m.tif")
raster2 = arcpy.Raster("C:\Users\XXX\Desktop\Raster_test\Producers_2008_56m.tif")
# Execute Plus
outPlus = Plus(raster1, raster2)
# Save the output 
  • Although I can't confirm this is the case for this tool, please see this answer to How to reduce Polygon to Raster (Conversion) bit depth? which suggests that there is no way to control bit-depth in some ArcGIS tools.
    – Midavalo
    Commented Feb 5, 2016 at 20:52
  • Thanks for the reply, I haven'y found a direct answer to my question online but reading about similar issues your suggestion may be the culprit. Commented Feb 5, 2016 at 21:16

1 Answer 1


Once you did your analysis you can Copy your output with arcpy.CopyRaster_management. Where you can specify bit depth through the pixel_type arg. For example - arcpy.CopyRaster_management("inrast","outrast","","","-9999", "","","8_BIT")

You can then delete the earlier output to cleanup. enter image description here

  • 1
    Thanks for the reply, worked like a charm! I replaced the Output.save() with the arcpy.CopyRaster_management() Commented Feb 6, 2016 at 0:17
  • great!, if this worked please tick the "accepted answer" green tick, so other users can see the question as an accepted answer. Cheers
    – yanes
    Commented Feb 8, 2016 at 18:41

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