Color spectrum files .CLR are used to define a spectrum, or continuous gradation of colors. This is specified by a series of anchor points with associated colors. The colors between anchor points are interpolated from the nearest anchor points.
The basic format consists of an ASCII file with header information on the first line. Subsequent lines specify anchors points, one anchor point per line.
The header consists of the following space-delimited fields:
Element |
Description |
Id |
case-sensitive string "ColorMap" without the quotes |
Version |
format version number, this should be set to 1 or 2 |
InterpMethod |
interpolation method between anchors, set to 0 |
ColorNodes |
the number of color nodes |
OpacityNodes |
the number of opacity nodes |
Subsequent lines define the anchor points, one per line. Each line in the Color section has the following space-delimited fields:
Element |
Description |
Position |
The position is the floating point value proportion of the colormap (from 0 to 1). Positions must be specified in increasing order from 0 to 1, and the 0 and 1 positions must be specified in the file. |
Red |
red color component (0 to 255) |
Green |
green color component (0 to 255) |
Blue |
blue color component (0 to 255) |
Each line in the Opacity section has the following space-delimited fields:
Element |
Description |
Position |
The position is the floating point value proportion of the colormap (from 0 to 1). Positions must be specified in increasing order from 0 to 1, and the 0 and 1 positions must be specified in the file. |
Opacity |
The opacity is the floating point value corresponding to the opacity at the node (from 0 to 1) |
Examples
In the following example, the anchor points are at 0, 50, and 100. The zero position is a slightly transparent blue, the 50 percent anchor is mostly transparent green, and the 100 percent position is fully opaque yellow.
ColorMap 2 0 3 3
0 |
0 |
0 |
255 |
|
.5 |
0 |
255 |
0 |
|
1 |
255 |
255 |
0 |
|
0 |
|
|
|
0.78431372549020 |
.5 |
|
|
|
0.07843137254902 |
1 |
|
|
|
1 |
It is also possible to have coincident anchor points in a color file. Anchors and colors are interpreted in order from 0 percent to 100 percent. In the case of coincident points, you can create maps with distinct boundaries, similar to the example shown here. This colormap has a fixed 0.2 Opacity.
ColorMap 2 0 4 2
0 |
255 |
0 |
0 |
|
50 |
255 |
255 |
0 |
|
50 |
0 |
0 |
255 |
|
100 |
255 |
255 |
255 |
|
0 |
|
|
|
0.2 |
1 |
|
|
|
0.2 |
The following example shows the format of the Rainbow colormap with a fixed 1.0 Opacity:
ColorMap 2 0 6 2
0 |
153 |
102 |
255 |
|
.2 |
0 |
0 |
255 |
|
.4 |
0 |
255 |
0 |
|
.6 |
255 |
255 |
0 |
|
.8 |
255 |
102 |
0 |
|
1 |
255 |
0 |
0 |
|
0 |
|
|
|
1 |
1 |
|
|
|
1 |
See Also