Bitwise Left Shift (Spatial Analyst)

Summary

Performs a Bitwise Left Shift operation on the binary values of two input rasters.

Illustration

 OutRas = BitwiseLeftShift(InRas1, 1)

Usage

• Two inputs are necessary for this bitwise operation to take place.

• The order of inputs is relevant for this tool.

• If an input is floating-point, the values are converted to integer values through truncation before the bitwise operation is performed.

• In bitwise operations:

• Binary values are stored in two's complement.
• The tools work on 32-bit integers.
• The leftmost bit position is reserved for the sign (positive or negative) of the value. If the integer is positive, the bit position is 0; if it's negative, the bit position is 1.

• The Bitwise Left Shift operation does no wrapping of bits. The leftmost bit is dropped.

• In Map Algebra, the equivalent operator symbol for this tool is "<<" (link).

Syntax

BitwiseLeftShift (in_raster_or_constant1, in_raster_or_constant2)
 Parameter Explanation Data Type in_raster_or_constant1 The input on which to perform the shift.A number can be used as an input for this parameter, provided a raster is specified for the other parameter. To be able to specify a number for both inputs, the cell size and extent must first be set in the environment. Raster Layer | Constant in_raster_or_constant2 The input defining the number of positions to shift the bits. A number can be used as an input for this parameter, provided a raster is specified for the other parameter. To be able to specify a number for both inputs, the cell size and extent must first be set in the environment. Raster Layer | Constant

Return Value

 Name Explanation Data Type out_raster The output raster. The cell values are the result of a Bitwise Left Shift operation on the inputs. Raster

Code Sample

BitwiseLeftShift example 1 (Python window)

This example left-shifts the values of the first input by the number of bits defined by the second input, and outputs the result as a TIFF raster.

```import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outBitwiseLS = BitwiseLeftShift("degs", "negs")
outBitwiseLS.save("C:/sapyexamples/output/outbitls.tif")```
BitwiseLeftShift example 2 (stand-alone script)

This example left-shifts the values of the first input by the number of bits defined by the second input.

```# Name: BitwiseLeftShift_Ex_02.py
# Description: Performs a Bitwise Left Shift operation on the binary
#              values of two input rasters
# Requirements: Spatial Analyst Extension
# Author: ESRI

# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import *

# Set environment settings
env.workspace = "C:/sapyexamples/data"

# Set local variables
inRaster1 = "degs"
inRaster2 = "negs"

# Check out the ArcGIS Spatial Analyst extension license
arcpy.CheckOutExtension("Spatial")

# Execute BitwiseLeftShift
outBitwiseLShift = BitwiseLeftShift(inRaster1, inRaster2)

# Save the output
outBitwiseLShift.save("C:/sapyexamples/output/outlshift")```

Licensing Information

ArcView: Requires Spatial Analyst
ArcEditor: Requires Spatial Analyst
ArcInfo: Requires Spatial Analyst

6/29/2011