Image service layer properties
Layer properties for most image services
The image service layer has layer properties similar to other layers in ArcGIS. Like a raster dataset layer, the Layer Properties dialog box contains the General, Source, Extent, Display, Symbology, and Key Metadata tabs. These tabs are similar to those for the raster dataset layer and other layers; however, the Display tab has one or two additional options.
Some image services may be cached. When you add a cached image service to ArcMap, the capabilities are limited. You can still use the Identify tool, but you cannot change some of the properties, such as the mosaic method. A cached image service provides better display performance and is ideal as a base image layer. If you want to access it as a dynamic image service (which allows you to modify its properties), you can. Right-click the image service layer in the table of contents and uncheck Enable Cache View Mode. To reenable and use this image service as a cached service, just check this option back on.
The options on the Display tab include the following:
- A check box to allow interactive display when using the Effects toolbar. If checked, the Effects toolbar allows you to interactively adjust the brightness or contrast of a layer. This option controls how the layer behaves if you use the Effects toolbar to modify contrast, brightness, or transparency. If unchecked, the layer will be updated only when you complete using the controls on the Effects toolbar.
- A check box to display the service resolution in the table of contents. The service resolution is the ratio of screen pixels to image cells at the current map scale. It helps you determine whether you are close to displaying the maximum resolution of the raster.
- A drop-down menu that allows you to choose which resampling method will be used on the imagery that is displayed. The options include nearest neighbor, bilinear interpolation, cubic convolution, and majority.
- Text boxes allowing you to specify the percentages used for contrast, brightness, and transparency of the layer:
- Contrast—Specifies the contrast percentage for the layer. The default and neutral contrast is 0 percent. You can type any value between 100 and -100.
- Brightness—Specifies the brightness percentage to be used for the layer. The default normal brightness is 0 percent. You can type any value between 100 and -100.
- Transparency—Specifies the transparency percentage for the layer. This enables you to see the underlying layers. Type any value between 0 and 100 percent. Type 0 if you do not want any transparency.
- A drop-down menu and text box to specify the compression applied to transmitted data. This transmission compression can be preset in the source to an image service, but you can always change this. A highly compressed image is transmitted faster than an uncompressed image; however, the image quality may not be as good.
- None—No compression is applied to the imagery, which provides the highest quality but results in the maximum volume of data transfer across the network.
- LZ77—An efficient lossless compression method recommended for imagery with similar pixel values (discrete data), such as scanned maps or results of classifications.
- JPEG—An efficient compression method that can often compress imagery by about three to eight times with little degradation of the image quality. When choosing the JPEG method, you can also edit the quality by typing a value from 0 to 100. A value of 80 tends to retain image quality while providing approximately 8x compression.
- LERC—An efficient lossy compression method recommended for data with a large pixel depth, such as float, 32-bit, 16-bit, or 12-bit data. When choosing this method, you need to specify the quality value, which represents the maximum error value that is applicable per pixel (not an average for the image). This value is specified in the units of the mosaic dataset. For example, if the error is 10 centimeters and the mosaic dataset is in meters, enter 0.1.
LERC compresses better (5 to 10 times) and faster (5 to 10 times) than LZ77 for float data and is better with integer data. When using integer data, and the error limit specified is 0.99 or less, LERC is considered a lossless compression.
- A check box to allow viewing the footprints for each raster dataset in the image service and a symbol selector button to allow changing the symbology. Optionally, you can choose to only view the primary rasters; therefore, service overview footprints will not be displayed. (This is only available when the source to the image service is a mosaic dataset.)
The Symbology tab is similar to the raster dataset layer. The renderers that apply to the image service will be available, just as they are with raster datasets. You can change the renderer, change the stretch applied to the histogram, and alter the background color and NoData representation.
Additional layer properties for the image service
Server Functions tab
The Functions tab is present if the publisher of the image service added functions. These functions can be one function or a chain of functions represented as a single item. These functions can be used to process the data on the server before displaying it in ArcMap.
To choose a function, click the Function drop-down list and choose an option. The description and any help for this function (generated by the creator of the function) will be displayed (if it exists).
Image services can have a default function that will be applied automatically. You can change it or set it to None if you wish to remove it.
The Return raw pixel value when using Identify tool checkbox allows you to return the raw pixel value or the rendered pixel value. By default the checkbox will be unchecked, therefore returning the rendered pixel value.
Additional layer properties for the mosaic dataset source
When the image service is created from a mosaic dataset (not a single raster dataset), additional layer properties are presented on several other tabs, including the Mosaic, Selection, Fields, Definition Query, Status, and Time tabs.
The Mosaic tab is available when the source of an image service is a mosaic dataset (not a single raster dataset). The mosaicked image displayed from an image service can be created from a number of input rasters. The mosaic method defines how the mosaic is created from different rasters, such as By Attribute where a field containing values is used to sort the images, or Closest to Center, where the image closest to the center of the display is on top. The mosaic operator allows you to define how to resolve the overlapping cells, such as choosing a blending operation.
The available mosaic methods are defined as part of the image service properties and may not all appear to the client. The mosaic methods include
- By Attribute—Enables raster ordering based on a defined metadata attribute (from the Order Field) and its difference from a base value (defined in the Order Base Value text box).
- Closest to Center—Enables rasters to be sorted based on a default order where rasters that have their centers closest to the view center are placed on top.
- Closest to Nadir—Enables rasters to be sorted by the distance between the nadir position and view center. This is similar to the Closest to Center method but uses the nadir point to a raster, which may be different than the center, especially for oblique imagery.
- Closest to Viewpoint—Orders rasters based on a user-defined location and nadir location for the rasters using the Viewpoint tool.
- North-West—Enables raster ordering in a view-independent way, where rasters with their centers to the northwest are displayed on top.
- Seamline—Cuts the raster using the predefined seamline shape for each raster using optional feathering along the seams and orders images based on the SOrder field in the attribute table.
- Lock Raster—Enables a user to lock the display of single or multiple rasters based on the ObjectID defined in the Lock Raster ID text box.
- None—Orders rasters based on the order (ObjectID) in the mosaic dataset attribute table.
The mosaic operators include
- First—The overlapping areas will contain the cells from the first raster dataset listed in the source.
- Last—The overlapping areas will contain the cells from the last raster dataset listed in the source.
- Min—The overlapping areas will contain the minimum cell values from all the overlapping cells.
- Max—The overlapping areas will contain the maximum cell values from all the overlapping cells.
- Mean—The overlapping areas will contain the mean cell values from all the overlapping cells.
- Blend—The overlapping areas will be a blend of the cell values that overlap; this blend value relies on an algorithm that is weight based and dependent on the distance from the cells to the edge within the overlapping area.
The Order Ascending check box controls the expected ordering of the images defined by the mosaic methods. Ascending will order the images as expected. Descending (unchecked) will reverse the order. For example, if the mosaic method is Closest To Center and the check box is unchecked (Descending), then the image furthest from the center will be displayed first.
The Reset button on the Mosaic tab will change the mosaic method settings back to their defaults.
The Selection tab allows you to alter how the footprint features will appear when selected.
The Fields tab displays the attribute fields that are transmitted with the image service. This tab is present when the image service contains multiple images and fields that can be queried. You can modify the fields by defining an alias for the field name. You can also reorder how fields will appear in the attribute table or choose to not display certain fields.
Definition Query tab
The Definition Query tab allows you to build a query to define a subset of a raster dataset that will be displayed in the image service. This tab is present when the image service contains multiple images and fields that can be queried. You can use Query Builder to build a query using a Structured Query Language (SQL) expression.
The Status tab allows you to examine the specific information about the image returned by the image service. This information includes the extent, the number of rows and columns of the image, the number of bands, a bit depth, and the size of the transmitted data. This tab is present when the image service contains multiple images.
If time can be enabled on this image service, you can enable it from this tab.