Displaying image layers

NoteNote:

The functionality described in this topic is available in Portal for ArcGIS 10.2.1 and later releases.

Using the map viewer, you can create and display your imagery on the web. As the author of a web map, you decide how the rest of the world will visualize your imagery.

When you add an image layer to a web map, the map initially uses the default display settings of the image service. If you want to change the appearance and ordering of the images in the display, you can change the image display, the image display order, and the image quality.

Image display

You can change the image display by using a predefined template or setting the band combination and stretch parameters.

Using a predefined template

When you publish an image service, you can predefine the image display with templates. You might use a predefined template for several reasons:

  • Display a clear and good view of the data
  • Display the images without clouds
  • Highlight certain features within the image

You can choose any of the predefined templates that best suits your web map.

Follow these steps to choose a predefined image display template.

Steps:
  1. Open the web map with the image layer you want to change in the map viewer.
  2. Click the Contents button in the Details panel.
  3. Click the arrow to the right of the layer name and click Image Display. The Image Display pane appears in the left side of the map viewer.
  4. Click the Renderer drop-down arrow and choose the display template you want to use.
  5. Click the Apply button.

The web map displays the image as set by the template you choose. These templates cannot be edited within the web map.

Using the user-defined renderer

The band combination allows you to specify which bands are displayed using the red, green, and blue color composite scheme. The different color combinations display your imagery with various color effects. You can display your data in a natural color (red, green, and blue), which displays the layer as you would normally see it. Other color combinations can highlight vegetation, urban areas, water, and other features.

The stretch parameters improve the appearance of your image by using various contrast enhancements. The following contrast enhancements determine the range of values that are displayed.

  • None—No additional image enhancements will be performed.
  • Minimum and Maximum—Display the entire range of values in your image.
  • Standard Deviation—Display values between a specified number of standard deviations.
  • Percent Clip—Set a range of values to display. Use the two text boxes to edit the top and bottom percentages.

You can also make additional adjustments to the dynamic range adjustment (DRA) and the gamma factor.

  • Dynamic Range Adjustment—Performs one of the above stretches but limits the range of values to what is currently in the display window. This option is always turned on if the image service does not have global statistics.
  • Gamma—Stretches the middle values in an image but keeps constant the extreme high and low values.

Follow these steps to change the image display.

Steps:
  1. Open the web map with the image layer you want to change in the map viewer.
  2. Click the Contents button in the Details panel.
  3. Click the arrow to the right of the layer name and click Image Display. The Image Display pane appears in the left side of the map viewer.
  4. Click the Renderer drop-down arrow and choose a user-defined image display.
  5. Adjust the Red, Green, Blue composite with the bands you want to display.
  6. Click the Stretch drop-down arrow and choose the stretch type to use.
    • None
    • Minimum and Maximum
    • Standard Deviation
    • Percent Clip
    1. Additionally, adjust any of the parameters for that particular stretch.
  7. Click the Apply button.

The web map displays the image with the user-defined parameters you set.

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 a user browses the service. When creating a web map, you select how the map will display for your audience. You can determine 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 areas of images that overlap one another.

As the author, you set the Priority Ordering Method; this controls which images are visible and the image order. 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 visiblity setting is always honored except when the A list of images option is chosen.

Check the Reverse the order box to reverse the order the priority sets.

After setting the Priority Ordering Method, there may be instances where two or more images overlap. You can resolve overlapping areas with the following settings:

Follow these steps to change the image priority order:

Steps:
  1. Open the web map with the image layer you want to change in the map viewer.
  2. Click the Contents button in the Details panel.
  3. Click the arrow to the right of the layer name and click Image Display Order. The Image Display Order pane appears in the left side of the map viewer.
  4. Select the method to prioritize imagery.
  5. Optionally, reverse the order, if necessary, by clicking the Reverse the order box.
  6. Select the method for resolving overlapping pixels.
  7. Click the Apply button.

The web map displays the images with the visibility and priority parameters you set.

Setting image quality

There are tradeoffs between performance and image layer quality because they are inversely related. Higher-quality images will be larger files and will affect performance speed. Performance is also dependent on your connection speed. There are several options designed to meet your needs and bandwidth capabilities.

In general, use the Quality or Balanced option. If you are on a network with low bandwidth, choose the Performance option. Note that choosing Performance will cause transparent pixels to be blacked out.

Follow these steps to change the image quality.

Steps:
  1. Open the web map with the image layer you want to change in the map viewer.
  2. Click the Contents button in the Details panel.
  3. Click the arrow to the right of the layer name and click Image Quality.

    The Image Quality slider appears in the map viewer.

  4. Use the slider to select the compression level.

The web map displays the image with the selected compression quality chosen.

Filter images

When you have multiple images in your image service, you can use attribute queries to filter the images displayed. Filtering image layers works similarly to filtering feature layers. For example, if you are working with the entire Landsat archive, but only want to see cloud-free images from Landsat-7 before its scan-line corrector went off, you could do that with a filter. One thing to note about image filtering is that the map scale may affect the visibility of filtered images.

To learn more about filtering, see Applying filters.

Show table/table options

You can display the table of the image layer. 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:

To learn more about tables, see Showing tables.

Legend

If your image service is shared on an ArcGIS 10.2 server or later, you can display a legend in your web map. The legend shows by default; however, there is an option to hide it.

To learn more about legends, see Viewing a legend.

3/24/2014