WaveFormColormap

DESCRIPTION

WaveFormColormap is an IRIS Explorer module for creating color maps. Ramp waves of variable frequency are used to establish a relationship between data values and colors. Colors may be specified in the RGB (Red, Green, Blue), HLS (Hue, Lightness, Saturation), and HSV (Hue, Saturation, Value) color spaces. WaveformColormap's output is a one dimensional floating point lattice of 4-tuples, of length 256. Each entry in the output lattice is a color vector with Red, Green, Blue, and Opacity components. Opacity here is 1 minus Transparency, and is set to the constant value one. The 256 color values are mapped uniformly on the minimum and maximum data domain values.
Palette Window
GenerateColormap has a Palette window to show the current colormap.
Color Sliders
WaveFormColormap uses six parameters to specify the evolution of colors over a range of data values. Two controls are used for each parameter in the current color space. The first control is the initial value of the parameter, and the second is the rate of change applied to it over the map. When the controlled parameter reaches its limit of zero or one, it is wrapped back into the space. This way, bands of color may be repeated over the map.
Color Space
The Color Space option menu chooses either the RGB, HLS, or HSV color space. When the color space is changed, the sliders control new parameters, and the output map changes.
Data Range
The two dials select the Minimum and Maximum of the domain of the color map. The defaults are zero and one, respectively.

EXAMPLES

Rainbow
The default controls for WaveFormColormap operate in HSV space. Hue is set by the first two sliders to start at zero (Red), and increase at the rate of 0.9. By the end of the map, the Hue parameter has risen to 0.9 (magenta). The other two parameters, Saturation and Value, are set to values of one. Because their rates are zero, the color maintains an equal Saturation and Value across the map.
Cool Ice
Change the color space to HLS. Set the Hue to 0.65 (Blue), with a small negative (-0.1) rate of change. Use the second two sliders to start at a medium Lightness (0.5), and move up to white by the end (rate equal 0.5). Leave the last two controls set for a constant Saturation of one. These settings give a Cool Ice map, useful for indicating decreasing temperature.
Hot Iron
Still in HLS space, set Hue at zero, with a small positive rate (0.2). Set the initial Lightness to zero, and let it increase to max at the end of the range (rate equal one). Again leaving Saturation at a constant one, results in a Hot Iron color map, approximating the black body curve for thermal emission. This map is useful for representing increasing temperature.
Contours
In HLS space, set Hue to its defaults: initial Value of zero, and rate of 0.9 to take it nearly through the spectrum. Set initial Lightness to zero, and use a rate of five. Leave Saturation at a constant value of one. This map gives five sharply defined lightness bands, which are made distinct by their unique hues. A map of this kind can be used to introduce simulated contouring in a rendered image.
WaveFormColormap borrows code from xloadimage to initialize color visuals, and therefore must present this copyright notice:

Copyright 1989, 1990, 1991 Jim Frost

Permission to use, copy, modify, distribute, and sell this software and its documentation for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation. The author makes no representations about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty.

THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

INPUTS

WIDGETS

Port: First Value
Type: Slider

Port: First Rate
Type: Slider

Port: Second Value
Type: Slider

Port: Second Rate
Type: Slider

Port: Third Value
Type: Slider

Port: Third Rate
Type: Slider

Port: Window
Type: Drawing Area

Port: Color Space
Type: Option Menu
Menu Item: RGB
Menu Item: HLS
Menu Item: HSV

Port: Min Domain
Type: Dial

Port: Max Domain
Type: Dial

OUTPUTS

Port: Colormap
Type: Lattice
Constraints: 1-D
Constraints: 4-vector
Constraints: float
Constraints: uniform

KNOWN PROBLEMS

UNIX ports only: When using X Pseudo-Color Visuals with limited bit planes, WaveFormColormap can fail to allocate the color cells required for its display, and fail to execute.

SEE ALSO

GenerateColormap, Contour, PyrToGeom, LatToGeom, VolumeToGeom, Render.
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© The Numerical Algorithms Group Ltd, Oxford UK. 2000

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