Note:
This functionality is currently only supported in Map Viewer Classic (formerly known as Map Viewer). It will be available in a future release of the new Map Viewer.
Using Map Viewer Classic, you can modify the display of your imagery in your web maps. As the author of a map, you decide how the imagery in the map is presented. You can modify the display settings for map image layers, ArcGIS Server image services, and hosted imagery layers.
When you add an imagery layer to a map, the map initially uses the default display settings of the imagery layer. To change the display settings, you can modify the image display, the image display order, or the image quality.
Image display
The options for displaying imagery layers depend on the type of raster or imagery data contained in the layer and the source of the layer. Different display options are called renderers. For example, the Stretch renderer uses the histogram of pixel values in a single-band raster to enhance the display of continuous data. Alternatively, the Classify renderer allows you to group ranges of pixel values into classes and assign colors to the individual classes.
ArcGIS Enterprise image services are sometimes published with processing templates, which appear as predefined renderers in the map. In these cases, you can select from one of the predefined renderers, or you can choose the User Defined Renderer in the image display options to provide your own settings for display.
When modifying display settings, the rendering and symbology options available to you in the map depend on the input data.
RGB composite
Rendering imagery data using the red, green, and blue (RGB) color composite allows you to use information from multiple bands in your multiband imagery to highlight specific features in the imagery. For example, you can use a natural color composite where the red, green, and blue channels are populated with the red, green, and blue sensor bands to render the image as you would see it naturally. You can also use other combinations to highlight green vegetation, water, or urban areas.
To modify the image display using RGB composite symbology, complete the following steps:
- Verify that you are signed in and open the map in Map Viewer Classic.
- Click Details, and click Contents.
- Browse to the imagery layer for which you want to adjust the display, click More Options
, and click Image Display. - If the imagery layer is an image service with predefined templates, select User Defined Renderer from the Renderer drop-down menu.
- Under RGB composite, select the bands you want to display in the red, green, and blue channels, respectively.
- Optionally, do any of the following:
- Select a stretch type from the Stretch Type drop-down menu.
- Check the Dynamic range adjustment box to perform the selected stretch operation while limiting the range of values to what is currently in the display window. This option is always turned on if the imagery layer does not have global statistics.
- Use the Gamma slider to modify the gamma value, which stretches the middle values in an image but keeps the extreme high and low values constant.
The available contrast enhancements determine the range of values that are displayed.
- Click Apply to apply the image display options to the layer, click Reset to return to the default display options, or click Close to close the Image Display tab without saving your choices.
Stretch
Applying a stretch to continuous data allows you to apply various color ramps and enhance the contrast in your imagery layer. Stretching is helpful when you want to make certain features in a continuous dataset more obvious. For example, you can apply a stretch to clearly show areas of high elevation compared to low elevation in a digital elevation model (DEM).
To modify the image display using Stretch symbology, complete the following steps:
- Verify that you are signed in and open the map in Map Viewer Classic.
- Click Details, and click Contents.
- Browse to the imagery layer for which you want to adjust the display, click More Options , and click Image Display.
- Do one of the following:
- Select the Stretch option from the Renderer drop-down menu.
- If the imagery layer is an image service with predefined templates, select User Defined Renderer from the Renderer drop-down menu, and select Stretch from the Symbology Type drop-down menu.
- Select a stretch type from the Stretch Type drop-down menu.
The following options are available:
- None—No additional image enhancements will be performed.
- Minimum and Maximum—Display the entire range of values in your image. Edit the values in the statistics table to make additional changes as needed. These are available only when the Dynamic range adjustment check box is cleared.
- Standard Deviation—Display values between a specified number of standard deviations.
- Percent Clip—Set a range of values to display, and exclude the highest and lowest pixel values from the stretch. Use the two text boxes to edit the top and bottom percentages.
- Optionally, if Stretch Type is set to an option other than None, do one or both of the following:
- Check the Dynamic range adjustment box to perform the selected stretch operation while limiting the range of values to what is currently in the display window. This option is always turned on if the imagery layer does not have global statistics.
- Use the Gamma slider to modify the gamma value, which stretches the middle values in an image but keeps the extreme high and low values constant.
- Optionally, if your imagery layer is a single-band image or raster, select a color ramp from the Color Ramp drop-down menu.
- Click Apply to apply the image display options to the layer, click Reset to return to the default display options, or click Close to close the Image Display tab without saving your choices.
Unique values
Rendering your imagery using unique values is useful for displaying thematic or categorical data. This display option is supported for single-band imagery layers that were published with a raster attribute table. You can base the unique values rendering on one or more attribute fields in the dataset. If the raster attribute table has red, green, and blue values specified in respective fields, the dataset will display using those colors by default. This display type is often used with thematic data such as land cover or risk zones.
To modify the image display using Unique Values symbology, complete the following steps:
- Verify that you are signed in and open the map in Map Viewer Classic.
- Click Details, and click Contents.
- Browse to the imagery layer for which you want to adjust the display, click More Options , and click Image Display.
- Do one of the following:
- Select the Unique Values option from the Renderer drop-down menu.
- If the imagery layer is an image service with predefined templates, select User Defined Renderer from the Renderer drop-down menu, and select Unique Values from the Symbology Type drop-down menu.
- Select the field you want to map from the Field drop-down menu.
- Select a color ramp from the Color Ramp drop-down menu.
- Optionally, edit the text in the Label column and the colors in the Symbol column.
- Click Apply to apply the image display options to the layer, click Reset to return to the default display options, or click Close to close the Image Display tab without saving your choices.
Classify
The Classify option allows you to group pixel or cell values into a specified number of classes and display each class with a given color. This option is supported for single-band imagery layers. For example, you can classify a temperature raster into regions of low, moderate, and high temperatures, and then add colors to distinguish the classes. If the imagery layer contains continuous data and a histogram has not been calculated, it will be calculated when the classify renderer is selected.
To modify the image display using Classify symbology, complete the following steps:
- Verify that you are signed in and open the map in Map Viewer Classic.
- Click Details, and click Contents.
- Browse to the imagery layer for which you want to adjust the display, click More Options , and click Image Display.
- Do one of the following:
- Select the Classify option from the Renderer drop-down menu.
- If the imagery layer is an image service with predefined templates, select User Defined Renderer from the Renderer drop-down menu, and select Classify from the Symbology Type drop-down menu.
- Select the field to use to classify the pixels from the Field drop-down menu.
The pixel value field, Value, is the default field.
- Select the classification method to use to classify pixels from the Method drop-down menu.
The following options are available:
- Natural Breaks—The class breaks are determined statistically by finding adjacent feature pairs between which there is a relatively large difference in data value.
- Equal Interval—The range of cell values are divided into equally sized classes where you specify the number of classes.
- Quantile—Each class contains an equal number of cells.
- Defined Interval—Specifies an interval to divide the range of cell values, and the number of classes will be automatically calculated.
- Manual Interval—Create the class breaks manually by typing in the pixel value ranges in the class table.
- Specify the number of groups of pixel values, or classes, to create in the Classes text box.
- Select a color ramp from the Color Ramp drop-down menu.
- Optionally, edit the text in the Label column and the colors in the Symbol column.
If you edit the pixel values in the class table, the Method selection automatically changes to Manual Interval, since you are now specifying pixel value ranges manually.
- Click Apply to apply the image display options to the layer, click Reset to return to the default display options, or click Close to close the Image Display tab without saving your choices.
Shaded relief
Shaded relief is supported for imagery layers containing elevation data. This option generates a representation of the terrain by applying built-in color ramps on the terrain's hillshade, which is useful for highlighting changing terrain. For example, you can apply shaded relief to clearly show areas of high elevation compared to low elevation in a digital elevation model (DEM).
To modify the image display using Shaded Relief symbology, complete the following steps:
- Verify that you are signed in and open the map in Map Viewer Classic.
- Click Details, and click Contents.
- Browse to the imagery layer for which you want to adjust the display, click More Options , and click Image Display.
- Do one of the following:
- Select the Shaded Relief option from the Renderer drop-down menu.
- If the imagery layer is an image service with predefined templates, select User Defined Renderer from the Renderer drop-down menu, and select Shaded Relief from the Symbology Type drop-down menu.
- Select a Hillshade Type and adjust the associated settings.
The Traditional hillshade type allows you to change the following settings:
- Azimuth—The sun's relative position along the horizon.
- Altitude—The sun's angle of elevation above the horizon.
- Z Factor—The scaling factor used for converting the elevation unit or for adding vertical exaggeration for visual effect.
- Scaling—The pixel size power and factor, which determines how the z factor will scale the shaded relief result.
- The Multidirectional hillshade type allows you to change the Z Factor setting and the Scaling setting.
- Select a color ramp from the Color Ramp drop-down menu.
- Click Apply to apply the image display options to the layer, click Reset to return to the default display options, or click Close to close the Image Display tab without saving your choices.
Colormap
Colormap symbology is supported on imagery layers that were published with a colormap. It uses the red, green, and blue values inside the colormap to display a single-band imagery layer. It also allows you to assign labels for each class.
To modify the image display using Colormap symbology, complete the following steps:
- Verify that you are signed in and open the map in Map Viewer Classic.
- Click Details, and click Contents.
- Browse to the imagery layer for which you want to adjust the display, click More Options , and click Image Display.
- Do one of the following:
- Select the Colormap option from the Renderer drop-down menu.
- If the imagery layer is an image service with predefined templates, select User Defined Renderer from the Renderer drop-down menu, and select Colormap from the Symbology Type drop-down menu.
- Edit the Label column as necessary for generating a new legend.
- Click Apply to apply the image display options to the layer, click Reset to return to the default display options, or click Close to close the Image Display tab without saving your choices.
Use a predefined template
Imagery layers generated from image services are often created with one or more processing templates associated with the dataset. Processing templates are preset display settings or raster function chains associated with the raster dataset. For example, the Seafloor Temperature (°C) imagery layer on ArcGIS Living Atlas is published with a cartographic renderer as well as a renderer that converts Celsius to Fahrenheit, and one that converts Celsius to Kelvin. These are not separate image services, but rather it is one image service that can be displayed with different processing options already applied. You can choose to display the imagery layer with any of the predefined templates.
Note:
As a consumer of the image service, you may be limited to viewing the templates that were created with the image service.
To use a predefined processing template to display imagery, complete the following steps:
- Verify that you are signed in and open the map in Map Viewer Classic.
- Click Details, and click Contents.
- Browse to the imagery layer for which you want to adjust the display, click More Options , and click Image Display.
- From the Renderer drop-down menu, select the predefined processing template to use to render the imagery layer.
- Click Apply to apply the image display options to the layer, click Reset to return to the default display options, or click Close to close the Image Display tab without saving your choices.
Image display order
An image service published from a mosaic dataset contains one or more images. These images are mosaicked on the fly and behave like a single image when you browse the service. For example, the USA NAIP Imagery: Natural Color imagery layer from ArcGIS Living Atlas is published from a mosaic dataset.
When working with these types of imagery layers in a web map, you can modify the image order and how to resolve overlapping areas. Image order refers to how to select an image when there are multiple images over the same area. You can also determine how to display the areas where images overlap one another in the imagery layer.
To change the image display order for a mosaic dataset imagery layer, complete the following steps:
- Verify that you are signed in and open the map in Map Viewer Classic.
- Click Details, and click Contents.
- Browse to the imagery layer for which you want to change the image order and click More Options > Image Display Order.
- In the Image Display Order pane, specify the method you want to use to prioritize imagery.
The available options are as follows:
- Only scale—Use this option to prioritize the image order by the scale of the images. For images that are at the same scale, the ObjectID in the image attributes determines their display order.
- An attribute—Select an attribute to determine the image order. The image with the highest value according to its attribute will be displayed on top. For example, if you want to show the most recent images, you can display the images based on their acquisition date. Use the calendar to select the acquisition date. Another common attribute to use is the percentage cloud cover to get the clearest image possible.
- Image center closest to the view center—As your audience browses through a mosaicked raster layer, the images that are displayed will change. The images with their image centers closest in distance to the center of the screen display on top. This is useful if your audience is interested in viewing features from a more persistent point of view.
- Fixed order with the most North West on top—The order is based on the center of each image's distance to the northwest corner of the mosaicked raster layer. Since this presents a static display, it is useful when you do not want the images to change as you roam across the mosaic.
- Sensor location closest to view center—Display the images with the least distortion. When a sensor captures an image, the point directly overhead of the image is known as the nadir point, which tends to have the least distortion, and effects—such as building lean—are minimized. The images with their nadir point closest in distance to the center of the screen are displayed on top.
- Defined seamlines—You must have seamlines already created if you want your audience to have access to this option. Images are prioritized based on your existing seamlines. If you choose this option, you should use Blend of pixel values to resolve any overlapping pixels.
- A list of images—If you're interested in a small number of images, you can explicitly list them using a comma-delimited list in the order you want them to be displayed. This method bypasses image visibility constraint and forces the listed images to display at any scale, for example, 1, 2, 5, 7, 9.
Note:
Images in an image service are visible at certain scales. The visibility range corresponds to the minimum pixel size (MinPS) and maximum pixel size (MaxPS) in the image attributes. The visibility setting is always honored except when the A list of images option is chosen. - Optionally, you can reverse the order of priority by checking the Reverse the order box.
- Specify the method for resolving overlapping pixels.
The available options are as follows:
- Only highest priority—Display the pixel value from the image that has the highest priority as set by priority ordering method.
- Minimum of pixel values—Display the lowest pixel value.
- Maximum of pixel values—Display the highest pixel value.
- Average of pixel values—Display the mean pixel value.
- Blend of pixel values—Use the blend option for overlapping areas to create a smooth transition along seamlines.
- Click Apply to apply your changes.
Image quality
You can change the image quality for dynamic imagery layers. To modify the image quality, you must modify the compression algorithm used to render the imagery layer. Higher quality images will result in larger files and will affect performance speed. There are three image quality options available, and your selection depends on your requirements and bandwidth.
To change the image quality of an imagery layer, complete the following steps:
- Verify that you are signed in and open the map in Map Viewer Classic.
- Click Details, and click Contents.
- Browse to the imagery layer for which you want to change the image quality and click More Options > Image Quality.
- Use the slider to select the compression level.
The following options are available:
- Performance—Compresses into a JPEG format at 50 percent quality. Assuming the original image has dimensions of 1,034 by 721 (approximately 2 MB), the transmitted size using this option is only 62K. This is recommended if you are on a network with low bandwidth. This option does not support any transparency, so areas of no data will be displayed in black.
- Quality—Compresses into a PNG32 format when there are NoData pixels present in the current view and creates a JPEG compression at 95 percent quality when there are no transparent pixels. Assuming the original image has dimensions of 1,034 by 721 and no transparent pixels, the transmitted size using this option is 277K.
- Balanced—Compresses into a PNG32 format when there are NoData pixels present in the current view and compresses into a JPEG format at 75 percent quality when there are no transparent pixels. Assuming the original image has dimensions of 1,034 by 721 and no transparent pixels, the transmitted size using this option is 99K.
- Click Apply to apply your changes.
Filter image layers
For imagery layers containing multiple images, you can use attributes to filter the images to be displayed. Filtering is supported for ArcGIS Enterprise image services published from a mosaic dataset or ArcGIS Enterprise hosted imagery layers generated from an image collection.
Filter using the Filter window or with the Image Filter pane.
- The Filter dialog box allows you to filter the imagery layer based on attributes and display all images that meet the filter criteria, across the full extent of the imagery layer.
- The Image Filter pane allows you to filter the imagery layer based on attributes and return all images from a geographic area of interest. The geographic extent of the search is limited to the visible display in the map.
Applying the filter returns the selected images in the Image Filter pane, and you can configure the results to display thumbnails or attributes to help narrow down your selection. After making a selection, you can then create a layer and add it to the Contents pane.
Filter
To display all images that meet certain criteria, across the full extent of the imagery layer, complete the following steps:
- Verify that you are signed in and open the map in Map Viewer Classic.
- Click Details, and click Contents.
- Browse to the imagery layer you want to filter and click Filter
. - Create your definition expression.
- Expressions use the general form of <Field_name> <Operator> <Value, Field or Unique>. The <Field_name> metadata attribute is what you'll use to filter, and the <Operator> attribute constrains the settings. The choice of operators depends on the attribute you choose.
- You can create one expression, multiple expressions, or one or more sets of expressions. A set is a grouping of expressions, for example, you can display imagery having an Acquisition Date after 3/17/2000 and before 9/30/2000 and shown in the following image. To create a set of expressions, click Add a set.
- If you have more than one expression, choose to display features in the layer that match All or Any of your expressions. All requires that all the criteria you have specified must be true. Any means that only one of your expressions must be true for the features to display. All or Any of your expressions can be applied to individual expressions, a set of expressions, or all of the expressions comprising your filter.
- For the field part of the expression, click the Field drop-down arrow and choose the field you want to query against from the list.
- For the operator part of the expression, click the Operators drop-down arrow and choose an operator from the list.
- To filter based on a specific value, choose Value and enter a value in the field. The input box varies depending on the field type.
- To compare the value in one field with the value in another field, choose Field, click the drop-down arrow, and choose the field for your expression.
- To filter based on a specific value in the field you've selected for your expression, choose Unique and select a unique value from your field. If this option is not available, restrictions may apply.
Note:
Unique value filters are not supported on date fields.
- To delete an expression in the filter, click the Delete button
to the right of your expression.
- Click Apply Filter to display the filtered images defined by the expressions in your filter.
Image Filter
To select images using the current display extent and attribute information, complete the following steps:
- Verify that you are signed in and open the map in Map Viewer Classic.
- Click Details, and click Contents.
- On the map, zoom to the area of interest.
- In the Contents pane, browse to the imagery layer you want to filter and click More Options > Image Filter.
- In the Image Filter pane, use the Attribute box to select the attribute and value to use to filter the images.
The resulting images are displayed in the Image Filter Results box.
- Optionally, use the following tools when you're selecting the images:
- Configure filter results—Configure the information displayed in the card. You can select up to four fields to be displayed, with an option to display thumbnails associated with each result.
- Select all—Select the maximum allowable number of images from the result, or unselect all images with one click. The maximum number of images selected is determined by the Max mosaic image count property of the service.
- Sort images—Sort the results in ascending or descending order based on the attribute field selected in the filter.
- Zoom to selected images—Zoom to the extent of the selected images.
- When you are finished, select the images you want to display from the results and click Add as a New Layer option to save the new layer and add it to the contents pane of the map as a layer.
The new layer is added to the Contents pane.
- Click Done to close the Image Filter pane and return to the Map Viewer Classic Contents pane.
Note:
The Image Filter pane works in conjunction with the layer Filter dialog box. If a layer filter is set on the image layer, the Image Filter option honors the filter query and works only with the images that are returned by the service for that query. This allows you to further refine your selection for the geographic area of interest.
Multidimensional filter
If your imagery layer is multidimensional, you can use the multidimensional filter to specify the variable and dimension value to display in the map. For example, the Sea Surface Temperature (°C) imagery layer from ArcGIS Living Atlas is a multidimensional imagery layer.
To apply a multidimensional filter, complete the following steps:
- Verify that you are signed in and open the map in Map Viewer Classic.
- Click Details, and click Contents.
- Browse to the multidimensional layer you want to filter and click More Options > Multidimensional Filter.
- Select the variable to display from the drop-down menu.
Choose Default to use the variable configured in the service. Default means there is no client-side variable filtering. This can be due to the server having a default variable configured through processing templates or a processing result derived from multiple variables.
- Check the dimensions to define the variable and use the calendar or drop-down menu to select the values.
Note:
You need to disable the time or other dimension animations from the layer before you can set the corresponding dimensions to display a specific value or range.
- Click Apply to apply the multidimensional filter.
Change the style of vector field data
You can symbolize image services with U-V or magnitude and direction information using vector symbols, such as arrows. The symbol size and color represent the magnitude. The angle represents the flow direction.
To modify the display of vector field data, complete the following steps:
- Verify that you are signed in and open the map in Map Viewer Classic.
- Click Details, and click Contents.
- Browse to the vector field layer in the Contents pane and click Change Style
. - Make any of the following changes:
- Symbol—Choose the type of symbol you want to use to display the data. Options include Simple Scalar, Single Arrow, Wind Barbs, Beaufort Wind scale, Ocean Currents with either 4 or 9 classes, and Classified Arrows. All the symbols except Simple Scalar use the size or color of the symbol to represent the magnitude of the data and the rotation angle of the symbol to represent its flow direction. Descriptions of each symbol are included in the drop-down menu.
- Direction represents flow—Choose to display the direction of the symbols in meteorological or oceanographic preference. Meteorologists display the data based on the direction from which air is flowing. Oceanographers, on the other hand, display data based on the direction water is flowing.
- Symbol density—Scale the patterns you are observing by moving the slider toward sparse or dense. As you move the slider toward sparse, each symbol will represent a larger area and, therefore, a larger pattern. A denser setting allows you to see patterns that are localized and smaller, as each symbol represents the data over a smaller area.
- Symbol scaling—Scale the symbols by moving the slider toward minimum or maximum. Use the advanced settings to set a more precise scale range.
- Advanced Settings—Set a precise range for the symbols by converting the magnitude and setting the minimum and maximum range. These settings affect the minimum and maximum symbol size because the size uses the converted magnitude unit. Limit the range of data that is displayed by setting a minimum and maximum value. Data outside of the range is symbolized using the minimum and maximum values.
- Click Apply to apply your changes.
Configure time and dimension animation
You can animate imagery layers with time or other dimensions enabled with the appropriate settings.
Enable time animation and settings
For imagery layers with a time dimension, you can use the time slider and time settings to control how to animate images across a time period. You must enable the time animation options for the imagery layer.
Enable dimension animation and settings
For an imagery layer with dimensions other than time, you can use the dimension slider to select the dimensions you want to animate. Common dimensions include elevation, depth, and pressure. For example, the HYCOM - Sea Water Salinity imagery layer from ArcGIS Living Atlas shows salinity at multiple depths, in addition to multiple times.
- Dimension—Set the dimension on which you want to display the variable in the animation.
- Reverse Animation—Change the direction of the dimension animation. You can set the animation to display from maximum to minimum dimensional values, or the reverse.
- Define Range—Set a range of values using the dimension slider. Uncheck this box to work with one slice at a time.
- Playback Speed—Set the animation speed.
- Dimension Range—This box is checked by default, and all slices are available for visualization. Uncheck the box to input specific values for the start and end points.
- Interval—This is similar to a time step in time animation; however, it is expressed in the units of the dimension rather than time. For example, when visualizing a variable at different depths, set the Interval to 100 meters to display the layer that represents every 100 meters of depth.
To use and configure the dimension slider and animation options, use the following steps:
- Add the multidimensional imagery layer to the map.
- If necessary, browse to the imagery layer in the Contents pane and click More Options > Enable Dimension Animation.
- Use the dimension slider to select the dimension value you want to display in the map.
- Click Play/Pause to play an animation of the imagery layer at each dimension value.
- Click Previous or Next to change the display by one dimension value.
- To modify the animation settings, click the Configure button and modify any of the following options:
- Dimension—Set the dimension on which you want to display the variable in the animation.
- Reverse Animation—Change the direction of the dimension animation. You can set the animation to display from maximum to minimum dimensional values, or the reverse.
- Define Range—Set a range of values using the dimension slider. Uncheck this box to work with one slice at a time.
- Playback Speed—Set the animation speed.
- Dimension Range—This box is checked by default, and all slices are available for visualization. Uncheck the box to input specific values for the start and end points.
- Click OK to apply your changes, or click Cancel to exit the Dimension Settings dialog box without saving your changes.
Table options
You can display a table of an imagery layer generated from a mosaic dataset. The table has metadata for each image, which can be useful for deciding which categories to use when filtering. You can also use the table to do the following:
- Show selected records or Show all records—Show only the records you have selected from the layer or table, or show all records.
- Center on the selection—Center on the selected records in your layer.
- Clear Selection—Clear the current imagery selections. They will remain visible on your map and in the table.
- Show/Hide columns—Choose which columns to display in the table.
- Filter—Set the filter to use attribute queries to filter the displayed images.
- Select visible images—Select the images that are visible on the map.
- Display all images—Display all the images from your layer on your map.
- Display selected images—Display only the images you have selected.
When you work with an imagery service composed of many images, you may want to select one or a few particular images to display. You will need to incrementally filter the images you want to display, lock the display to the images you want, and reset the display so that no images are selected.
The following steps show you how to perform this workflow.
- Filter your imagery layer first by applying a filter, by using the table to Show Visible Images, or by clicking a point on the map when the table is displayed. Once you have filtered images, use Table Options to show the selected records.
- Refine your selection by clicking records in the table. You can use the Ctrl key to select multiple items. Choose Show Selected Records again using the table options.
- Use Display Selected Images to lock the images.
- Reset the display to show all images by selecting Display All Images.
Legend
If your image service is published on an ArcGIS 10.2 or later server, you can display a legend in your map. The legend is displayed by default; however, there is an option to hide it.