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Raster

Summary

Creates a raster object that can be used in Python scripting or in a Map Algebra expression. A raster object is a variable which references a raster dataset.

A raster object can be created in two ways. You can create a raster object by supplying the path to an existing raster on disk, or it can be the result of any Map Algebra statement that results in a raster output.

License:

An ArcGIS Spatial Analyst extension is necessary to execute Map Algebra statements.

Discussion

The raster object created from existing data can be used in subsequent Map Algebra expressions and will have all the associated raster properties and methods.

# out_raster is a resultant raster object
out_raster = Raster("c:/data/inraster")

Any Spatial Analyst tool or operator (see Working with operators) that produces an output raster to the left of the equal sign creates a raster object. For example, in the following expression, out_raster is a raster object.

out_raster = Slope("inelevation")

When a raster object is returned from a Map Algebra expression, by default, the object (the variable and associated dataset) is temporary.

The temporary dataset associated with a raster object can become permanent with the following mechanisms:

  1. By calling the save method on the raster object.
  2. Call Make Permanent by right-clicking on the layer with an associated raster object in the TOC and specifying an output name.
  3. Saving the map project (.MXD, .3DD, and so on) that contains any layers with associated raster objects.

    In case 3, the dataset referenced by the raster object will automatically be permanently saved to disk with a default name.

If the referenced raster is not made permanent by any of the three cases above, the variable and the referenced raster dataset will be deleted when the variable goes out of scope, such as when a stand-alone script is completed or ArcGIS is closed. When a raster object references permanent data on disk, the data is not deleted.

Certain operators exist in both Map Algebra and in Python. If you want an operator to work on rasters (as opposed to scalars) the input rasters must be cast as a raster object by calling the Raster class constructor: Raster("inRaster").

# The Spatial Analyst plus operator is used on the input rasters creating
# an output raster object
out_raster = Raster("input1") + Raster("input2") 
																																												
# The Python plus operator is used on numbers creating a scalar variable
out_var = 4 + 7 

# When there is a mix of rasters with numbers the Spatial Analyst
# operator is used creating an output raster object
out_raster = Raster("input") + 10

Certain properties associated with the raster object are only available if the referenced raster dataset is permanent. When the referenced raster dataset is temporary, these properties will be assigned None. The affected properties are catalogPath, compressionType, format, hasRAT, name, and path.

Once permanent, the referenced raster dataset cannot return to the temporary state.

Syntax

 Raster (inRaster)
ParameterExplanationData Type
inRaster

The input raster dataset.

Raster

Properties

PropertyExplanationData Type
bandCount
(Read Only)

The number of bands in the referenced raster dataset.

Integer
catalogPath
(Read Only)

The full path and the name of the referenced raster dataset.

String
compressionType
(Read Only)

The compression type. The following are the available types:

  • LZ77
  • JPEG
  • JPEG 2000
  • PACKBITS
  • LZW
  • RLE
  • CCITT GROUP 3
  • CCITT GROUP 4
  • CCITT (1D)
  • None

String
extent
(Read Only)

The extent of the referenced raster dataset.

Extent
format
(Read Only)

The raster format

  • BIL—Esri Band Interleaved by Line file
  • BIP—Esri Band Interleaved by Pixel file
  • BMP—Bitmap graphic raster dataset format
  • BSQ—Esri Band Sequential file
  • DAT—ENVI DAT file
  • GIF—Graphic Interchange Format for raster datasets
  • Grid—Esri Grid raster dataset format
  • IMAGINE Image—ERDAS IMAGINE raster data format
  • JP2000—JPEG 2000 raster dataset format
  • JPEG—Joint Photographic Experts Group raster dataset format
  • PNG—Portable Network Graphic raster dataset format
  • TIFF—Tag Image File Format for raster datasets

String
hasRAT
(Read and Write)

Identifies if there is an associated attribute table: True if an attribute table exists or False if no attribute table exists.

Boolean
height
(Read Only)

The number of rows.

Integer
isInteger
(Read Only)

The integer state: True if the raster dataset has integer type.

Boolean
isTemporary
(Read Only)

The state of the referenced raster dataset: True if the raster dataset is temporary or False if permanent.

Boolean
maximum
(Read Only)

The maximum value in the referenced raster dataset.

Double
mean
(Read Only)

The mean value in the referenced raster dataset.

Double
meanCellHeight
(Read Only)

The cell size in the y direction.

Double
meanCellWidth
(Read Only)

The cell size in the x direction.

Double
minimum
(Read Only)

The minimum value in the referenced raster dataset.

Double
name
(Read Only)

The name of the referenced raster dataset.

String
noDataValue
(Read Only)

The NoData value of the referenced raster dataset.

Double
path
(Read Only)

The full path and name of the referenced raster dataset.

String
pixelType
(Read Only)

The pixel type of the referenced raster dataset. The types are

  • U1—1 bit
  • U2—2 bits
  • U4—4 bits
  • U8—Unsigned 8 bit integers
  • S8—8 bit integers
  • U16—Unsigned 16 bit integers
  • S16—16 bit integers
  • U32—Unsigned 32 bit integers
  • S32—32 bit integers
  • F32—Single precision floating point
  • F64—Double precision floating point

String
spatialReference
(Read Only)

The spatial reference of the referenced raster dataset.

SpatialReference
standardDeviation
(Read Only)

The standard deviation of the values in the referenced raster dataset.

Double
uncompressedSize
(Read Only)

The size of the referenced raster dataset on disk.

Double
width
(Read Only)

The number of columns.

Integer

Method Overview

MethodExplanation
save ({name})

Permanently saves the dataset the raster object references.

Methods

save ({name})
ParameterExplanationData Type
name

The name to assign to the raster dataset on disk.

String

Code sample

Raster example 1

Creates a Raster object from a raster dataset and gets properties for analysis.

import arcpy

my_raster = arcpy.Raster('elevation')
my_min = my_raster.minimum
my_max = my_raster.maximum
my_area = (my_raster.width * my_raster.height) * my_raster.meanCellWidth
Raster example 2

Creates a Raster object, gets properties, creates a random error raster (+/- 3 feet), adds it to an elevation raster, and converts its units from feet to meters.

import arcpy
from arcpy.sa import *

elev_raster = Raster('c:/data/elevation')
my_extent = elev_raster.extent
my_cellsize = (elev_raster.meanCellHeight + elev_raster.meanCellWidth) / 2
res01 = arcpy.CreateRandomRaster_management("", "error3", "UNIFORM 0.0 3.0",
                                            my_extent, my_cellsize)
elev_meters = (elev_raster + Raster(res01)) * 0.3048
elev_meters.save("c:/output/fgdb.gdb/elevM_err")