Raster symbolizer

The raster symbolizer styles raster (coverage) layers. A raster is an array of information with each cell in the array containing one or more values, stored as “bands”.

The full syntax of a raster symbolizer is:

symbolizers:
- raster:
    opacity: <expression>
    channels:
      gray:
        <channel_options>
      red:
        <channel_options>
      green:
        <channel_options>
      blue:
        <channel_options>
    color-map:
      type: <ramp|interval|values>
      entries:
      - [color, entry_opacity, band_value, text_label]
    contrast-enhancement:
      mode: <normalize|histogram>
      gamma: <expression>

where:

Property

Required?

Description

Default value

opacity

No

Opacity of the entire display. Valid values are a decimal between 0 (completely transparent) and 1 (completely opaque).

1

channels

No

Selects the band(s) to display and the display method.

N/A

gray

No

Display a single band as a grayscale image. Cannot be used with red, green, and blue. The <channel_options> can be the band name or a mapping containing name: and contrast-enhancement: (optional).

1

red

No

Display three bands as an RGB image. Must be used with green, and blue. Cannot be used with gray. The <channel_options> can be the band name or a mapping containing name: and contrast-enhancement: (optional).

1

green

No

Display three bands as an RGB image. Must be used with red, and blue. Cannot be used with gray. The <channel_options> can be the band name or a mapping containing name: and contrast-enhancement: (optional).

2

blue

No

Display three bands as an RGB image. Must be used with red, and green. Cannot be used with gray. The <channel_options> can be the band name or a mapping containing name: and contrast-enhancement: (optional). See examples below.

3

color-map

No

Creates a mapping of colors to grid values. Can only be used with a single band.

N/A

type

No

Type of color mapping. Options are ramp, an interpolated list of values; interval, a non-interpolated list of values; and values, where values need to match exactly to be drawn.

ramp

entries

No

Values for the color mapping. Syntax is a list of tuples.

N/A

color

Yes

Color for the particular color map entry. Value is a standard color value.

N/A

entry_opacity

Yes

Opacity of the particular color map entry. Valid values are a decimal between 0 (completely transparent) and 1 (completely opaque).

N/A

band_value

Yes

Grid value to use for the particular color map entry. Values are data-dependent. Behavior at or around this value is determined by the color ramp type.

N/A

text_label

No

Label for the particular color map entry

Blank

contrast-enhancement

No

Modifies the contrast of the display

N/A

mode

No

Type of contrast enhancement. Options are normalize (stretches contrast so that the smallest and largest values are set to black and white, respectively) or histogram (produces equal number of content in the image at each brightness level).

normalize

gamma

No

Multiplier value for contrast adjustment. A value greater than 1 will increase darkness, while a value less than 1 will decrease darkness.

1

Examples

Enhanced contrast

This example takes a given raster and lightens the output by a factor of 2:

symbolizers:
- raster:
    contrast-enhancement:
      gamma: 0.5
../../../../_images/raster_brightness.png

Lightened image

Normalized output

This example takes a given raster and adjusts the contrast so that the smallest values are darkest and the highest values are lightest:

symbolizers:
- raster:
    contrast-enhancement:
      mode: normalize
../../../../_images/raster_normalize.png

Normalized image

Band selection

This example takes a raster with multiple bands and outputs band 2 as a grayscale image (This could be used to select a single band in a multi-band image to use with color-map):

name: raster
feature-styles:
- name: name
  rules:
  - symbolizers:
    - raster:
        opacity: 1.0
        channels:
          gray: 2
../../../../_images/raster_band_gray.png

Grayscale band selection

Band selection with contrast

This example takes an RGB raster, doubles the intensity of the red, and normalizes the green band:

name: raster
feature-styles:
- name: name
  rules:
  - symbolizers:
    - raster:
        channels:
          red:
            name: 1
            contrast-enhancement:
              gamma: .5
          green:
            name: 2
            contrast-enhancement:
              mode: normalize
          blue:
            name: 3
../../../../_images/raster_band_contrast.png

Band selection with contrast enhancement

Color ramp

This example shows a color ramp from red to green to blue, with raster band values from 0-200:

symbolizers:
- raster:
    color-map:
      type: ramp
      entries:
      - ['#FF0000', 1, 0, red]
      - ['#00FF00', 1, 100, green]
      - ['#0000FF', 1, 200, blue]

In this example, the grid values will have the following colors applied:

  • Less than or equal to 0 will have an output color of solid red

  • Between 0 and 100 will have an output color interpolated between red and green

  • Between 100 and 200 will have an output color interpolated between green and blue

  • Greater than 200 will have an output color of solid blue

../../../../_images/raster_map_ramp.png

Color map with ramp

Color intervals

The same example as above, but with the color-map type set to intervals:

symbolizers:
- raster:
    color-map:
      type: intervals
      entries:
      - ['#FF0000', 1, 0, red]
      - ['#00FF00', 1, 100, green]
      - ['#0000FF', 1, 200, blue]

In this example, the grid values will have the following colors applied:

  • Less than or equal to 0 will have an output color of solid red

  • Between 0 and 100 will have an output color of solid green

  • Between 100 and 200 will have an output color of solid blue

  • Greater than 200 will not be colored at all (transparent)

../../../../_images/raster_map_intervals.png

Color map with intervals

Color values

The same example as above, but with the color-map type set to values:

symbolizers:
- raster:
    color-map:
      type: values
      entries:
      - ['#FF0000', 1, 0, red]
      - ['#00FF00', 1, 100, green]
      - ['#0000FF', 1, 200, blue]

In this example, the grid values will have the following colors applied:

  • Equal to 0 will have an output color of solid red

  • Equal to 100 will have an output color of solid green

  • Equal to 200 will have an output color of solid blue

Any other values (even those in between the above values) will not be colored at all.

../../../../_images/raster_map_values.png

Color map with values

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