Color Reference

It can be useful to apply different colors to a Spacecraft based on a time sequence of events (for example, red for launch, yellow for ascent, and green once the spacecraft is on orbit). You can also illustrate the beginning and end of events by changing the color of a Spacecraft or GroundStation. In the example below, the Spacecraft color is changed to green when the Spacecraft is in contact with a GroundStation.

Color Systems

FreeFlyer allows users to manipulate colors through the following color systems:

•ColorTools object

oAllows you to directly specify the name of the desired color.

oDiscussed in detail below.

•RGB

oProvides access to the ratios of red, green, and blue components in the color.

oMore intuitive than Base 10 or Base 16.

•HSV

oIn the HSV color space, colors are determined by evaluating three components, namely:

▪Hue - ranging from 0 to 360, hue represents a color on the color wheel, where 0 corresponds to red, 120 corresponds to green, and 240 corresponds to blue.

▪Saturation - ranging from 0 to 1, saturation represents the amount of gray present, where 0 corresponds to pure gray, and 1 corresponds to the primary color.

▪Value or Lightness - ranging from 0 to 1, this represents the intensity of the color.

•L*A*B*

oIn the L*A*B* color space, colors are determined by evaluating three components, namely:

▪Lightness - ranging from 0 to 100, where 0 corresponds to black and 100 corresponds to white.

▪A* - green-red, negative numbers correspond to green, positive to red. Typically this runs from -100 to 100 or -128 to 127.

▪B* - blue-yellow, negative numbers correspond to blue, positive to yellow. Typically this runs from -100 to 100 or -128 to 127.

•Base 10

oLittle intuitive mapping to the color it represents.

•Base 16

oHexadecimal representation of the color.

oShows the red, green, and blue components on a scale of 0x00 to 0xFF (0 to 255).

oThe red component is specified at the right, green is in the middle, and blue is at the left.

oSo, 0xF0E1D2 has 0xD2 = (13*16+2) = 210 components of Red, 0xE1 = (14*16+1) = 225 components of Green, and 0xF0 = (15*16+0) = 240 components of Blue. This results in a light blue-gray.

The table below shows a comparison of the values of some basic colors in each of the systems supported by FreeFlyer.

Color	ColorTools	RGB	Base 10	Base 16
White	ColorTools.White	RGB(1,1,1)	16777215	0xFFFFFF
Black	ColorTools.Black	RGB(0,0,0)	0	0x000000
Red	ColorTools.Red	RGB(1,0,0)	255	0x0000FF
Green	ColorTools.Lime	RGB(0,1,0)	65280	0x00FF00
Blue	ColorTools.Blue	RGB(0,0,1)	16711680	0xFF0000
Yellow	ColorTools.Yellow	RGB(1,1,0)	65535	0x00FFFF
Cyan	ColorTools.Cyan	RGB(0,1,1)	16776960	0xFFFF00
Magenta	ColorTools.Magenta	RGB(1,0,1)	16711935	0xFF00FF
Gray	ColorTools.Gray	RGB(0.5,0.5,0.5)	8421504	0x808080

You can set colors for Spacecraft, GroundStation, Sensor, ProximityZone, PointGroup, Region, Star, Vector, and GraphicsOverlay objects, as well as some properties of the View, Plot, Grid, Console, and Watch windows. For example, you can set the tail color of a Spacecraft to green as follows:

The ColorTools Object

The ColorTools object allows you to easily specify and manipulate colors in FreeFlyer.

Using Color Names

The ColorTools object provides access to the standard set of named colors, as shown in the example below for the color "yellow":

The GetColorName and GetColorFromName methods allow users to determine the color value based on a known color name, and vice versa.

Accessing Color Components

The GetRedComponent, GetGreenComponent, and GetBlueComponent methods return a value between 0 and 1 for each component.

Accessing Colors in a Color Palette

The GetPaletteColors method returns the colors contained within the specified color palette.

ColorTools Palettes

Value	Palette Colors	Default Type
"Accessible"		Qualitative
"Bright"		Qualitative
"Classic"		Qualitative
"Dark"		Qualitative
"Light"		Qualitative
"Paired"		Qualitative
"Pastel"		Qualitative
"Blues"		Sequential
"CubeHelix"		Sequential
"Grays"		Sequential
"Greens"		Sequential
"Purples"		Sequential
"Reds"		Sequential
"Spectral"		Sequential
"BluePurpleYellow"		Diverging
"GreenCyanBlue"		Diverging
"GreenYellowRed"		Diverging
"PurpleBlueGreen"		Diverging
"YellowRedPurple"		Diverging
"BlueCyanGreen"		"Terrain"
"BlueYellowGreen"		"Terrain"
"BrownWhiteOrange"		"Terrain"
"GreenBrownWhite"		"Terrain"
"YellowTanBeige"		"Terrain"

Adjusting Brightness

The AdjustBrightness method takes an input color (dark olive green in the example below) and adjusts its brightness by a specified factor. If the factor is less than 1, the resulting color is darker; a factor greater than 1 results in a lighter color. A factor of 1 causes no change.

If any of the red, green, and/or blue components of the input color is equal to 1, the color cannot be brightened. Setting a brightness factor greater than 1 will have no effect.

// Create a "triangle strip" GraphicsOverlay with color based on dark olive green with a brightness factor between 0 and 2

GraphicsOverlay GO;

GO.ShapeType = "Triangle Strip";

For i = 0 to 1 step 0.1;

color = ColorTools.AdjustBrightness(ColorTools.DarkOliveGreen, i*2);

GO.AddOverlayElement(7000*cos(pi+i*2*pi), 7000*sin(pi+i*2*pi), -10000, color);

GO.AddOverlayElement(7000*cos(pi+i*2*pi), 7000*sin(pi+i*2*pi), 10000, color);

Map GO;

End;

Interpolating Colors

The InterpolateColorRGB method interpolates two or more colors given a designated weight in the RGB color space. The InterpolateColorHSV method interpolates two or more colors given a designated weight in the HSV color space. The InterpolateColorLAB method interpolates two or more colors given a designated weight in the L*A*B* color space. It should be noted, L*A*B* interpolation assumes that colors are in sRGB and use the standard D65 white point. In the example below, the colors crimson, chartreuse, dodger blue, and gold are interpolated into 100 unique colors.

// Create a "triangle strip" GraphicsOverlay with colors interpolated based on a set of 4 input colors

GraphicsOverlay GO;

GO.ShapeType = "Triangle Strip";

For i = 0 to 1 step 0.01;

color = ColorTools.InterpolateColorRGB({ColorTools.Crimson, ColorTools.Chartreuse, ColorTools.DodgerBlue, ColorTools.Gold}, i);

GO.AddOverlayElement(7000*cos(pi+i*2*pi), 7000*sin(pi+i*2*pi), -10000, color);

GO.AddOverlayElement(7000*cos(pi+i*2*pi), 7000*sin(pi+i*2*pi), 10000, color);

Map GO;

End;

Grayscale

The ConvertToGrayscale method gets the grayscale value of the specified color using the formula: 0.30 * R + 0.59 * G + 0.11 * B. The example below shows the grayscale equivalent of the dark olive green AdjustBrightness example above.

// Create a "triangle strip" GraphicsOverlay with color based on grayscale version of dark olive green with a brightness factor between 0 and 2

GraphicsOverlay GO;

GO.ShapeType = "Triangle Strip";

For i = 0 to 1 step 0.1;

color = ColorTools.AdjustBrightness(ColorTools.DarkOliveGreen, i*2);

color = ColorTools.ConvertToGrayscale(color);

GO.AddOverlayElement(7000*cos(pi+i*2*pi), 7000*sin(pi+i*2*pi), -10000, color);

GO.AddOverlayElement(7000*cos(pi+i*2*pi), 7000*sin(pi+i*2*pi), 10000, color);

Map GO;

End;

Color Reference

Color Systems

The ColorTools Object

Using Color Names

Accessing Color Components

Accessing Colors in a Color Palette

ColorTools Palettes

Adjusting Brightness

Interpolating Colors

Grayscale

See Also