Accessing individual raster bands using arcpy Raster class?

Question

I am working with rasters in arcpy and I am not able to access individual bands using the Raster class. The same code that worked about a year ago no longer works.

I should be able to access a single band of a raster like so:

Band3 = Raster(raster_filename + "/Band_3")

But the resulting Band3 variable has all 6 bands in the raster, not just band 3.

The "/Band_3" syntax appears to work fine in the Describe method in the first half of the following code but doesn't work in the Raster class later on:

    folder = r"C:\Users\elyons\Desktop\Spring_2018\Labs\New_LabData"

    import arcpy
    from arcpy.sa import *
    arcpy.CheckOutExtension("Spatial")

    arcpy.env.workspace = folder
    arcpy.env.overwriteOutput = True

    raster_filename = "Landsat.tif"

    #Create describe objects
    desc = arcpy.Describe(raster_filename)
    desc_band = arcpy.Describe(raster_filename + "/Band_3")

    #These are properties of the describe raster BAND object
    print "Height = " + str(desc_band.height)
    print "Width = " + str(desc_band.width)
    print "Resolution = " + str(desc_band.meanCellWidth)

    #This one is a property of the describe raster dataset object
    print "Number of Bands is = " + str(desc.bandCount)

    #Open bands as raster band objects
    Band3 = Raster(raster_filename + "/Band_3")

    #print number of bands
    print Band3.bandCount

    #Save the raster
    print "saving"
    Band3.save("savebandtest.tif")
    print "saved"


    arcpy.CheckOutExtension("Spatial")

The above code prints out the correct information for the describe objects and then prints 6 for Band3.bandCount, which is not right. It then saves a six band raster to the filename savebandtest.tif that is identical to Landsat.tif. I have tried different multiband rasters, different computers, getting the band name programatically, setting the working directory to the raster, forward slashes, backward slashes, everything I can think of.

Has the syntax changed for accessing single bands from multiband raster files? I can't find any mention of a change in the help.

Answer 1

It depends on whether your band names are actually "Band_1" to "Band_N" or something else like 'CoastalAerosol', 'Blue', 'Green', 'Red', etc...

If you want to access the bands by index, use the Make Raster Layer (Data Management) tool.

See also Access individual bands and use them in map algebra.

Answer 2

You can acess the individual bandnames using the Describe's children property.

desc = arcpy.Describe(raster)
for rband in desc.children:
    print rband.name

Answer 3

Hey I found that you actually need a backslash, in the python console the syntax looks something like:

out_raster = arcpy.ia.FocalStatistics(r"C:\Users\BigBoy\BigBoyTif.tif\Band_1",...

Meanwhile in geoprocessing it should be that the Input raster is

C:\Users\BigBoy\BigBoyTif.tif\Band_1