Change the symbology of imagery—ArcGIS AllSource

Depending on the type of imagery you're working with, there are a number of options for displaying and symbolizing it. Only symbology types that are valid for the data you've selected are presented. For example, you can display multispectral imagery using a three-band color composite—also known as an RGB composite—in which you use the available bands to highlight features of interest. You can also display the values along a color scheme to show the areas that are brighter than others. This is referred to as applying a stretch to a dataset. You can use the Classify and Discrete options to group continuous data into a limited number of groups. The Vector Field option allows you to display ocean and wind currents as arrows indicating magnitude and direction. This also works with a dataset that has vector (V) and unit vector (U) components.

Modify the appearance of an image layer

To change the appearance of an image layer, complete the following steps:

Click the Symbology button, located on the Raster Layer, Mosaic Layer, or Image Service Layer tab.
The Symbology pane appears.
Set the symbology parameters for the layer.
Click the lower half of the Symbology button to access additional symbology options.

In the Symbology pane, you can fine-tune the parameters that are specific to the symbology type you selected. You can also select other layers from the Contents pane and, without closing the Symbology pane, apply the same symbology to them.

There are minor, yet distinct, differences between the options for symbolizing imagery. The RGB, Unique Values, Stretch, Colormap, Classify, Shaded Relief, and Discrete options accomplish similar adjustments but in different ways. Stretch is the classic color scheme option; it takes the range of all the values in the data and stretches it to fit within a data type range. For example, 8-bit data is stretched from 0 to 255. Unique Values is similar, except the colors are not continuous. This is appropriate for qualitative data such as land cover. The Discrete color scheme is continuous, as is Stretch, but you specify how many colors it uses to display the data with no legend in the Contents pane. The pixel values are then grouped accordingly. Classify is similar to Discrete, except it includes the distribution of values and groups the values into the number of breaks or colors you want to display. A color map is useful when you want to select a color for each pixel value. These can be saved, imported, and exported for use with other datasets. The Vector Field option allows you to display phenomena—such as currents—as arrows, or vectors, in which the direction of the arrow indicates the direction of the current, and the size of the arrow is related to the force of the current. Vector Field symbology can be applied to a dataset with a magnitude and direction or a U and V component.

Save symbology settings as a template

You can save symbology settings as a template in the Symbology pane and reuse them as custom functions that can be applied from the Raster Functions pane. This generates a template that contains the appropriate functions to replicate the symbology used to display the layer of a raster dataset, mosaic dataset, or image service.

You can do the following with this template:

Use it as a processing template for a mosaic dataset. Open the Raster Type properties, click the Functions tab, right-click a template in Processing Template, and click Load.
Edit the function chain in a mosaic dataset or its items using the Edit Function Chain option from the layer context menu.

To save a template of symbology settings as a function that can be accessed from the Raster Functions pane, complete the following steps:

Note:

The raster function template (RFT) displays the raster layer as it appears using the RGB symbology. Once the RFT is applied, the result is processed and cannot be reverted to the original renderer.

Add a raster dataset, mosaic dataset, or image service to a map.
Click the Symbology button on the Raster Layer, Mosaic Layer, or Image Service Layer tab.
Modify the symbology, such as applying a stretch or using a different color scheme.
Click the Options button in the Symbology pane and choose Export as raster function template.
Provide a name for the template.
Choose a Custom Category and a Sub-Category value.
Provide Description text, choose a Type value, and click OK.

RGB

The color model RGB stands for red, green, and blue. RGB symbology allows you to create composite images by loading multispectral bands into each channel (R, G, and B). The various band combinations can help highlight specific features on the image.

Infrared, red, and green bands rendered as an RGB raster

Primary symbology options

Under Band Combinations, select the bands you want to display as red, green, and blue. To obtain a natural-looking image, match the red image band with the red video display channel, green with green, and blue with blue. You can also create other composites that highlight how features respond to various parts of the electromagnetic spectrum. For example, load the near-infrared band into the red drop-down list, the red band into the green drop-down list, and the green band into the blue drop-down list. This creates a color infrared composite that uses the strong reflection of vegetation in the near-infrared band and displays areas of high vegetation as red. An alpha band acts as a transparency mask, providing a transparency value for each pixel. An alpha band can be turned on or off for multiple-band raster datasets rendered with the RGB Composite renderer.

Check the Invert check box to invert each band to create a negative image.

Use Stretch Type to define the range of values to display. This is often used to eliminate extreme high and low values that represent noise in imagery. When you choose one of the options from the Stretch Type drop-down list, the parameters that you set here are used. The following are the Stretch Type options:

None—No stretch is applied to the layer, even if statistics exist. To display data other than 8-bit data, image values are linearly mapped between 0 and 255. None is a good choice if you want to examine absolute values in raster datasets.
Minimum Maximum—A linear stretch is applied based on the output minimum and output maximum pixel values, which are used as the endpoints for the histogram. For example, in an 8-bit dataset, the minimum and maximum values may be 33 and 206. A linear stretch is used to distribute the values across 256 values, from 0 to 255. In this example, 33 is mapped to 0, 206 is mapped to 255, and the values between these endpoints are linearly distributed. This increases the ability to see differences in values throughout the dataset.
Percent Clip—A percentage of the highest and lowest values are clipped and a linear stretch is applied to the remaining values across the available dynamic range of the data type. This reduces the effects of outliers in the datasets and enhances the remaining data.
Standard Deviation—A linear stretch is applied between the values defined by the standard deviation (n) value. For example, if you define a standard deviation of 2, the values beyond the second standard deviation become 0 or 255, and the remaining values are linearly stretched between 0 and 255.
Histogram Equalization—A nonlinear contrast stretch is applied in which the values are spread out throughout the bit depth range. This method is appropriate when there are many pixel values that are closely grouped.
Histogram Specification—The histogram is loaded from an .xml file. This allows you to edit the histogram in a piecewise fashion, in which you can assign a linear stretch to multiple ranges of values in the data.
Custom—A custom stretch is applied. This allows you to edit the histogram in a piecewise fashion, in which you can assign a linear stretch to multiple ranges of values within the data. This is the set stretch type when you create a custom stretch of any kind.
Esri—A sigmoidal stretch is applied, which makes it ideal for maintaining contrast in bright areas, such as an urban area surrounded by a desert.

Click the Histogram button Raster Histogram Stretch to view the histogram distribution of the pixels, and use the Minimum Maximum, Percent Clip, and Standard Deviation stretch types to view the pixel distribution and interactively set the minimum and maximum input values. When you edit the histogram, the Histogram button Open edited histogram is updated, indicating that it has been edited. See Raster histogram stretching for more information about the Histogram page.

Adjust the Gamma setting of the imagery to highlight the contrast of moderate pixel values.

There are two subtabs on the Primary symbology tab :

Statistics
Mask

Use the Statistics tab to specify how the data will be displayed. The Statistics drop-down menu contains the DRA (dynamic range adjustment), Dataset, and Custom options. When DRA is chosen, the statistics based on the current display extent are calculated as you zoom and pan the image. The Dataset option calculates the statistics for the entire dataset and uses those values regardless of the portion of the image that is displayed. You can also input custom statistics in the table using the Custom option. You can do this by importing the statistics from another dataset or importing an .xml file from the Options menu. When you're finished, you can save the custom statistics.

Use the Mask subtab to remove background values and set the NoData values. If you want to set the background value, you must do so for each band. Although these values are often the same for each band, they may change. Check the Display background value check box, provide the values that represent the background, and choose the background color. You can also choose a color for the NoData pixels. Click the Apply button to save the changes.

Advanced symbology options

When the RGB renderer is using a raster layer that has wavelength information in the metatdata, the Advanced symbology options tab RGB Band Selector is available. This page is helpful to select bands based on wavelength, such as hyperspectral imagery.

This tab provides two methods for setting the red, green, and blue bands. The top of the page shows which bands you want to display with the appropriate wavelength. The up and down arrows next to the band name allow you to fine-tune which band you want to choose. The bottom of the page shows a graphical view of the red, green, and blue bands along the electromagnetic spectrum. Here you can adjust the three bands close to the appropriate wavelength, and use the fine-tuning arrows, at the top of the page, to pick the specific band or wavelength.

The Show Band Names check box allows you to turn the band names on and off, within the Select by Wavelength (nm) portion of the page. This may be helpful when you use the Scaling drop-down list to zoom in to the wavelength graphic.

Use the Apply button to accept the updated band selections and have it persisted to the display. To return to the last persisted band combination, click the Reset button.