Drawing a continuous raster dataset

The Stretched renderer displays continuous raster cell values across a gradual ramp of colors. Use this renderer to display a single band or continuous data, such as in imagery, aerial photography, or elevation models.

You can make modifications to this renderer by accessing the layer's properties or using the Image Analysis window.

Note:

The Stretched renderer uses statistics to apply the stretch. When you display a raster dataset with statistics, they will be used. If the raster datasets do not have statistics, they will be generated from a subset of the data, but only for the purpose of displaying. To render the raster dataset, by taking into account all cell values, the raster dataset must have statistics.

Learn about calculating statistics

All renderers have an Import button. Click this button to import symbology from a raster layer file (*.lyr) or a raster layer that is currently in the table of contents. The current renderer must match the renderer of the imported layer.

Steps:

1. In the table of contents, right-click the raster layer that you want to display across a color ramp and click Properties.
2. Click the Symbology tab.
3. Click Stretched.
4. Optionally, if your raster dataset has multiple bands, choose the band you want to stretch.
5. Optionally, click the Label text boxes and type labels for the table of contents.

   You can make modifications to the values and labels. You can modify the values by clicking the Edit High/Low Values check box. This allows you to define the low and high values to be used, rather than using the raster layer's lowest and highest values.

6. Click the Color Ramp drop-down arrow and click a color ramp.

   Optionally, right-click the color ramp to

   • Toggle between a graphic view and text view.
   • Open the properties to modify specifics about how the color ramp is generated.
   • Save the color ramp.

7. Optionally, click the Display NoData as button to symbolize the NoData using a color.
8. Optionally, click the Stretch drop-down arrow and click the type of stretch you want to use.

   None	No stretch will occur. The pixel values will be mapped from the possible minimum and maximum values of the data type and depth stored in the raster to the beginning and end of the color ramp.
   Esri	The statistics and histogram is analyzed and a modified sigmoid stretch is applied. It uses an S curve to find a mean and helps to prevent pixel values to be stretched to the extremes. This method is used to provide a good overall stretch to imagery.
   Histogram Equalized	A histogram equalization contrast stretch will be applied. This method is good when there are a lot of pixel values that are closely grouped together.
   Minimum-Maximum	The minimum and maximum values of the calculated statistics will be used as the minimum and maximum values of the color ramp; all values in between will be interpolated linearly.
   Percent Clip	A stretch is applied without using the top and bottom extreme percent values. You need to specify the minimum and maximum percentage values to exclude from the stretch. Valid values for the minimum and maximum are 0 to 100.
   Standard Deviation	A standard deviation stretch will be applied. You can also specify the n value for the number of standard deviations to use. This method is used to emphasize how much feature values vary from the mean value; it is best when used on normally distributed data.
   Custom	A customized histogram stretch can be specified by clicking the Histogram button. Add breakpoints to the graph line by clicking inside the histogram. Move them to the required location in order to stretch particular values. Learn how to work with the histogram
   Histogram Specification	Allows you to load an XML file containing a customized histogram.

   Learn more about the stretches

9. Optionally, check Apply Gamma Stretch and type a gamma value.

   By applying the gamma stretch, you can control the overall brightness of an image.

   Valid gamma values are zero and above. If the gamma value is set too low, middle tones appear too dark; however, if the gamma value is set too high, middle tones appear too light, and the raster dataset looks bleached out.

   Gamma stretching is only valid with some renderers: None, Standard Deviation, and Minimum-Maximum.

10. Optionally, scroll down and click Statistics to change the statistics controlling how your data is displayed.

    Current Display Extent	Uses the statistics only from the pixels that are currently displayed in the display view. This allows for better contrast in areas where the pixel values are similar.
    Each Raster Dataset	Uses the statistics from the entire raster dataset. This ensures that the same statistics are used for each raster dataset.
    Image Service	Uses the statistics from the image service layer.
    Custom	Uses the statistics that you specify.

11. Optionally, check the Invert check box to invert the color ramp from high to low and vice versa.
12. Optionally, check the Display Background Value check box to use a specific color, or no color (transparent) for the background cell value you define.
13. Optionally, check the Use hillshade effect check box to display a DEM as a hillshade and modify the Z value if required.

    This option is simply an on-the-fly representation of a hillshade. To learn about other options, see Displaying a DEM with hillshading.

    The Z value can either be a conversion factor (if the vertical and horizontal units are not the same) or a vertical exaggeration. Learn about the z factor.

14. Click OK.

Tip:

You can quickly change the colors applied to a raster by clicking the color in the table of contents.

Note:

Statistics and histograms for raster catalogs cannot be generated in the Symbology tab. You need to use the Batch Calculate Statistics tool on each raster catalog item.