Styling a raster layer¶

Raster layers are composed of a grid of values in one or more bands. A grayscale image will have a single band, with each grid element containing the intensity at that pixel. An RGB image will have 3 bands, corresponding to red, green, and blue values. A raster can have any number of bands.

This raster layer has a single band. With the default raster symbolizer, it is drawn as a grayscale image.

Viewing the existing style¶

In the layers tab of Composer, click the style option for the dem layer to go to the style edit page. A simple default style is already associated with this layer:
```
name: raster
feature-styles:
- name: name
  rules:
  - symbolizers:
    - raster:
        opacity: 1
```
Default raster display

Adding contrast¶

If we want the land to show up better in the display, we can use the contrast-enhancement attribute:
```
name: raster
feature-styles:
- name: name
  rules:
  - symbolizers:
    - raster:
        opacity: 1
        contrast-enhancement:
          mode: histogram
          gamma: 4
```
This adjusts the contrast so each brightness level contains an equal amount of content, and darkens the resulting image by a factor of 4.

Added contrast

Creating a color map¶

The color-map attribute can be used to convert any single band of data into a colored image based on the band values.

Since contrast-enhancement cannot be used with color-map, remove it from the style. Replace it with a color map with the following intervals:

Color Values

'#0043C8' Less than 8080

'#00C819' Between 8080 and 100000
```
color-map:
  type: intervals
  entries:
  - ['#0043C8', 1, 8080, blue]
  - ['#00C819', 1, 100000, green]
```
Interval color map

The color map can also be used with type: ramp to create a gradient of colors between entries. Use this to create a basic colored elevation map with entries denoting ocean and four elevations:

Color	Value
`'#0043C8'` (ocean)	Less than `8080`
`'#3A3519'` (shore)	Between `8080` and `8100`
`'#4B4422'` (low elevation)	Between `8080` and `10000`
`'#857B54'` (mid elevation)	Between `10000` and `15000`
`'#D9D1A8'` (red)	Between `15000` and `30000`

color-map:
  type: ramp
  entries:
  - ['#0043C8', 1, 8080, ocean]
  - ['#3A3519', 1, 8100, shore]
  - ['#4B4422', 1, 10000, low]
  - ['#857B54', 1, 20000, mid]
  - ['#D9D1A8', 1, 60000, high]

Final style¶

The final style looks like:

name: raster
feature-styles:
- name: name
  rules:
  - symbolizers:
    - raster:
        opacity: 1
        color-map:
          type: ramp
          entries:
          - ['#0043C8', 1, 8080, ocean]
          - ['#3A3519', 1, 8100, shore]
          - ['#4B4422', 1, 10000, low]
          - ['#857B54', 1, 20000, mid]
          - ['#D9D1A8', 1, 60000, high]

../../../_images/raster_dem_brownscale.png

Simplified color map

Note

Download the final raster style

We have now styled all of our layers. Continue on to Composing a map for the final step in the process.