Colour Display Techniques Additive Colours

Subtractive Colours

Colour TriangleColour Cubes

HexagonHexcone

Hue, Intensity and SaturationChromo-Stereoscopy

Colour mixAdditive Primaries:

Red, Green and BlueSubtractive Primaries:

Yellow, Magenta and Cyan

The colour of an object is defined by the colour of light that it reflects.

Colour Cube

L & K 10.7

HexagonA hexagon is formed by the interception of the plane of projection with all six sides of the colour cube

Hexagon

R

Y

G

C

B

M

Perpendicular to the gray line

Hexcone

Hexcone: When the plane of projection is moved from the white to black along the gray line, successively smaller colour subcubes are intercepted and a series of hexagons of decreasing size are produced. The hexagonat white is the largest and the hexagon at black is reducedto a point. This series of hexagons define a solid called the hexcone

Hue: the angle around the hexagon. It gives the dominant color

Intensity: the distance from the zero intensity point along the gray line. It defines the brightness of a color

Saturation: the distance from the gray point at the centre aof the hexagon. It reveals the purity of a color

RGB to HIS transformation

R

G

B

I

H

S

Chromo-StereoscopyDepth perception can be created using a pair of glasses which have different refraction indices for different colours. Digital Elevation models (DEM) can be assigned with different coloursto create depth perception.

red green blue wavelength

Ref

ract

ion

inde

x

Chromo-Stereoscopy

Example:

Hue DEM, For depth perceptionIntensity TM for surface brightnessSaturation SAR for surface texture (terrain shadows, forest roughness)

This is a perfect combination to show the topography, surface features and natural shadows in one image

Chromo-StereoscopyExample II:

Hue DEM, for depth perceptionIntensity TM for surface brightnessSaturation constant

This combination is useful when only DEM and optical data are available. Surface features and terrain relief are shown very well using this combination

Chromo-StereoscopyExample III:

Hue DEM, for depth perceptionIntensity SARSaturation constant

This combination is useful to show terrain relief and shadows