Editing functions on a raster dataset

The same functions that are used within a mosaic dataset can be added to a raster dataset layer in ArcMap. Some functions are automatically added when using the options on the Processing section of the Image Analysis window. For example, when you click the Clip button , a new raster layer is added to the table of contents and this layer uses the Clip function. Anytime you use a button on the Image Analysis window that adds a function, a new temporary layer is added to the table of contents.

To see the function chain or to check if your raster layer uses a function, open the layer properties—if there is a Functions tab, then your raster layer uses a function. Click this tab to view or edit the function chain.

Adding a function

Each function in a function chain is represented by a function symbol .

To begin adding functions for the first time you need to click the Add Function button on the Image Analysis window. If the raster layer contains a Functions tab you can modify the chain and functions within that tab. If you wish to generate a new raster layer in the table of contents with an edited function chain, click the Function Editor button.

Getting to the function chain can vary, depending on if it exists. These steps describe how to add a function to a raster layer for the first time.

Steps:

1. In ArcMap, open the Image Analysis window (click Window > Image Analysis).
2. Select the layer in the Image Analysis window and click the Add Function button.

   The Raster Function Editor window opens containing a default function chain. The Identity function exists when there is no other function. Once you add a function, the Identity function disappears as it is no longer necessary.

3. Right-click the Identity function, click Insert, then click the function you want to add.

   When you add a function, it is inserted above the function you clicked.

4. Modify its settings and click OK.

   Once you click OK, the function chain will be validated. If the function you are adding invalidates the function chain it will not be added.

   You cannot drag and drop functions to change their position within the chain. You need to remove a function and add it to a new location if you want to move a function.

Editing a function

Steps:

1. You can access the function chain by doing the following:
   • Right-click the raster layer, click Properties, then click the Functions tab. This allows you to modify the raster layer's function chain.
   • Select the layer in the Image Analysis window and click the Add Function button. This will open the raster layer's function chain on the Raster Function Editor window, and once complete, a new layer will be added to the table of contents, thereby allowing you to compare the raster layer before and after the changes.
2. Open the function properties dialog box by doing either one of the following:
   • Double-click the function.
   • Right-click the function and click Properties.

For each function there can be several different tabs, depending on the requirements for the function. These include:

• The General tab describes the function. This tab is common to all functions. It is the location where you can define the output pixel type.
• A unique tab for each function contains the specific parameters for that function.
• The Output Info tab contains the property information for the raster that is being generated by the function.
• The Key Metadata tab contains any applicable information that is being passed from the inputs to the output raster.

Once done, close the dialog boxes.

Removing a function

Caution:

Be careful when removing functions. You could remove a function that will invalidate the function chain. There is no way to undo the edit once you've removed a function.

Steps:

1. You can access the function chain by doing the following:
   • Right-click the raster layer, click Properties, then click the Functions tab. This allows you to modify the raster layer's function chain.
   • Select the layer in the Image Analysis window and click the Add Function button. This will open the raster layer's function chain on the Raster Function Editor window, and once complete, a new layer will be added to the table of contents, thereby allowing you to compare the raster layer before and after the changes.
2. Right-click a function and click Remove.

Saving your layer

Once you've added functions to your raster layers you may want to save them. There are three options:

• Save the raster layer. Right-click the layer and click Save As Layer File.
• Save it in a mosaic dataset. Right-click the layer and click Data > Add To Mosaic Dataset.
• Save it as a new raster dataset. Right-click the layer and click Data > Export Data.