Polarity Glossary

Polarity Glossary

List of terms and definitions

Term	Definition
Max(R,G,B)	The maximum value of an RGB triplet. Max(0.1. 0.2, 0.3) = 0.3
Min(R, G, B)	THe minimum value of an RGB triplet. ALso equivelant ot the purity of that triplet
Purity	How close an RGB triplet is to the hull of it’s colour space. [0.0, 0.4, 0.6] is maximally pure as the red component is on the hull. A minimally pure colour is an achromatic triplet (R=G=B) as all the components are equally far from the hull
Normalize	Spread the image data to fill the range 0.0 - 1.0. To do this subtract the lowest none zero pixel value from all pixels and then multiply all pixels by 1 divided by the max pixel value
Offset	The base value compnent of an RGB triplet. E.G. [0.1, 0.2, 0.3] has an offset of [0.1, 0.1, 0.1]. An RGB triplet can be “offset” up or down by a set amount. E.G. we can offset [0.1, 0.2, 0.3] by +0.1 to get [0.2, 0.3, 0.4]
Gain	The reamining colour component of and RGB triplet after the offset has been removed. E.G. The gain component of [0.1, 0.2, 0.3] is [0.0, 0.1, 0.2]. A triplet can be gained by multiplying either component wise or all three components together (uniform)
Pictorial exposure	Changing the exposure of the image post formation. Increasing the pictorial exposure leads to a fogging of the image, a totally black stimuli would have an offset
Stimuli Exposure	Adjusting the energy in front of the camera either by add/removing light or changing the exposure time/aperture. A fully absorbative surface would remain at zero energy. This has to happen pre image formation otherwise the contrast of the image will fundamentally change and break the image