gamma.py

# Creates a gamma-corrected lookup table by @hexagon5un
# 04/23: updated file handle func and template strings for python 3, 
#        uses byte datatype instead of int,
#        uses PROGMEM for storing table in memory (accessed with pgm_read_byte in Arduino),
#        added explanatory comments and number padding (@matthewepler)

import math

def gamma(nsteps, gamma):
    gammaedUp = [math.pow(x, gamma) for x in range(nsteps)]
    return [x/max(gammaedUp) for x in gammaedUp]

def rounder(topValue, gammas):
    return [min(topValue, round(x*topValue)) for x in gammas]

if __name__ == "__main__":
    myGamma = 2.3 # usually a number between 1 and 3 with 2.0 - 2.3 being most common
    steps = 256   # bit resolution (8-bit = 256, 12-bit = 4096)
    maxVal = 255  # the maximum value, usually the same value as "steps" - 1

    # open a new file, write a header and declare a variable for the table
    output = open('gamma.h', 'w');
    output.write(f'const byte PROGMEM gamma[{steps}] = ')
    output.write('{\n')

    cols = 16    # number of columns to appear in the table
    colCounter = 0;
    totalCounter = 0;
    for value in rounder(maxVal, gamma(steps, myGamma)):
        # write the value, padded with spaces for readability
        output.write(f'{value:>3}')
        colCounter += 1
        totalCounter += 1

        if totalCounter < steps:
            # ensure last value in array is not followed by a comma
            output.write(',');

        if colCounter % 16 == 0:
            output.write('\n')
            colCounter = 0;

    output.write("};\n")
    output.close()