Colormap function

Overview

The Colormap function is a type of raster data renderer. It transforms the pixel values to display the raster data as either a grayscale or an RGB color image based on a color ramp or specific colors in a color map file. You can use a color map to represent analyzed data, such as a classified image or when displaying a topographic map (or an index color-scanned image).

Classified image

Topographic map

Color maps contain a set of values that are associated with colors used to display a single-band raster consistently with the same colors. Each pixel value is associated with a color, defined as a set of RGB values. Color maps are capable of supporting any bit depth except floating point. They also support positive and negative values and can contain missing color mapped values. When displaying a dataset with a color map containing missing values, the pixels with those missing values will not be displayed.

When the Colormap function is used, the dataset will be displayed using the color map renderer or a specified color ramp.

Notes

You can also input a .clr file or an .act file from Adobe Photoshop. The .clr file is an ASCII file containing the color map information for each pixel value on a separate line, formatted as pixel_value and associated red, green, and blue values. The following is an example of the contents of a .clr file:

1 255 0 0
2 100 0 100
3 50 200 10
4 45 60 100

You can create a .clr file from the Raster Properties dialog box. See Creating a color map (.clr) file for more information.

The .act file from Adobe Photoshop is a non-ASCII file. The first color in the table has a zero index, and the color is ordered as red, green, and blue. Each color is represented by three bytes, one byte each for red, green, and blue.

If you don' have a colormap and you don't want to create one, you can choose to use a color ramp to symbolize your values. Since there is no specific color tied to each value, this will render your data as if you are using the stretched renderer.

If a mosaic dataset is served as an image service, the publisher (or administrator) has the option to serve it using the color map or to convert the color map to an RGB image. The color map will automatically be converted to RGB when the image service is served using WMS or WCS.

Parameters

Parameter	Description
Input Raster	The input raster.
Color Scheme Type	Choose the type of color scheme to render your input raster Colormap—Use a pre-existing color map. Color Ramp—Use a color ramp.
Colormap	The following default color maps are available from the drop-down list: Elevation—A color map that gradually changes from cyan to purple to black. Gray—A color map that gradually changes from black to white. Hillshade— A colormap to visualize a hillshade product. It has a color scheme that gradually changes from black to white depending on topography. NDVI—A colormap to visualize vegetation. Values near zero are blue. Low values are brown. Then the colors gradually change from red, to orange, to yellow, to green, and to black as the vegetation index goes from low to high. NDVI2—A colormap to visualize vegetation. Low values range from white to green. Then the colors range from gray, to purple, to violet, to dark blue, and to black as the vegetation index goes from low to high. NDVI3—A colormap to visualize vegetation. Values near zero are blue. Then the colors gradually change from red, to orange, and to green as the vegetation index goes from low to high. Random—A random colormap. Additionally, you can browse to a pre-existing color map file that you have access to.
Colorramp	Choose a pre-existing color ramp or create your own color scheme.