GAMMA

Arduino Library for the GAMMA function to adjust brightness of LED's etc.

Description

This library is provides a gamma lookup class. It is typical used to change the intensity / brightness of a LED to match the human eye. When a LED is given 50% PWM it looks far brighter for the eye.

This lib provides a balance between an expensive math function and the speed of a lookup table.

The accuracy of the library depends on the size of the internal array. A size of 256 is the reference. Smaller arrays use interpolation and these interpolated values are good (< 1%) down to internal array size 16. The size can be as small as 2 which is pretty inaccurate. In this latter case the curve is approximated by only two linear interpolations. In short, choose the size that fits your application.

The library has a setGamma() function that allows an application to change the gamma value runtime. This allows adjustments that a fixed table does not have.

The class can be used to dump the internal table e.g. to place in PROGMEM.

Interface

Core functions

GAMMA(size = 32) constructor, gets the size of the internal array as parameter. The array is initialized with a gamma == 2.8 which is an often used value.
The default for size = 32 as this is a good balance between performance and size ot the internal array. The size parameter must be in {2, 4, 8, 16, 32, 64, 128, 256 }
setGamma(float gamma) calculates and fills the array with new values. This can be done runtime so runtime adjustment of gamma mapping.
This function relative quite some time.
getGamma() returns the set gamma value.
operator [] allows the GAMMA object to be accessed as an array. like x = G[40]; Makes it easy to switch with a real array.

Development functions

size() returns size of the internal array.
distinct() returns the number of distinct values in the table.
dump() dumps the internal table to Serial. Can be useful to create a direct usable array in RAM, PROGMEM or wherever.

Future ideas

look for optimizations
uint16 version?

Operation

See example

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