Define Overviews (Data Management)
Summary
Customize the way you generate overviews. This tool grants a greater deal of control than Build Overviews.
Usage
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This tool is used when there are specific parameters you need to set to generate your overviews, such as
- Defining the location to write the files
- Defining an extent that varies from the boundary
- Defining the properties of the overview images, such as the resampling or compression methods
- Defining the overview sampling factor
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Use the Build Overviews tool to generate the overviews after they've been defined with this tool.
You can use a polygon feature class to define the shape of the overview. An overview image will be created for every polygon in the feature class. Ideally, your feature class will be used to create one overview image. If you do not wish to use all the polygons in the feature class you can make a selection on the layer in the table of contents or use a tool such as Make Feature Layer to create a temporary layer representing only the desired polygons.
The default tile size is 128 by 128. The tile size can be changed in the Environment Settings.
This tool can take a long time to run if the boundary contains a large number of vertices.
Syntax
| Parameter | Explanation | Data Type |
in_mosaic_dataset |
The mosaic dataset that you want to build overviews on. | Mosaic Layer |
overview_image_folder (Optional) |
The folder or geodatabase to store the overviews. | Workspace |
in_template_dataset (Optional) |
A raster dataset or feature class to define the extent of the overviews. | Raster Layer; Feature Layer |
extent (Optional) |
Manually set the extent using minimum and maximum x and y coordinates. This is specified as space delimited in the following order: X-minimum X-maximum Y-minimum Y-maximum. The mosaic dataset boundary will determine the extent of the overviews if you do not define an extent. | Envelope |
pixel_size (Optional) |
If you prefer not to use all the raster's pyramids, specify a base pixel size at which your overviews will be generated. The units for this parameter are the same as the spatial reference of the mosaic dataset. | Double |
number_of_levels (Optional) |
Specify the number of levels of overviews that you want to generate overviews. A value of -1 will determine an optimal value for you. | Long |
tile_rows (Optional) |
Set the number of rows (in pixels) for each tile. Larger values will result in fewer, larger individual overviews, and increase the likelihood that you will need to regenerate lower level overviews. A smaller value will result in more, smaller files. | Long |
tile_cols (Optional) |
Set the number of columns (in pixels) for each tile. Larger values will result in fewer, larger individual overviews, and increase the likelihood that you will need to regenerate lower level overviews. A smaller value will result in more, smaller files. | Long |
overview_factor (Optional) |
Set a ratio to determine the size of the next overview. For example, if the cell size of the first level is 10, and the overview factor is 3, then the next overview pixel size will be 30. | Long |
force_overview_tiles (Optional) |
Generate overviews at all levels, or only above existing pyramid levels.
Overviews above pyramids Overviews at all levels | Boolean |
resampling_method (Optional) |
Choose an algorithm for aggregating pixel values in the overviews.
Nearest Bilinear Cubic | String |
compression_method (Optional) |
Define the type of data compression to store the overview images.
| String |
compression_quality (Optional) |
Choose a value from 1 - 100. Higher values generate better quality outputs, but they create larger files. | Long |
Code Sample
This is a Python sample for DefineOverviews.
import arcpy
arcpy.DefineOverviews_management("c:/workspace/fgdb.gdb/md01",
"c:/temp", "#", "#", "30", "6", "4000",
"4000", "2", "CUBIC", "JPEG", "50")
This is a Python script sample for DefineOverviews.
#Define Overviews to the default location
#Define Overviews for all levels - ignore the primary Raster pyramid
#Define Overviews compression and resampling method
import arcpy
arcpy.env.workspace = "C:/Workspace"
arcpy.DefineOverviews_management("DefineOVR.gdb/md", "#", "#", "#", "#",
"#", "#", "#", "#", "FORCE_OVERVIEW_TILES",
"BILINEAR", "JPEG", "50")