#!/usr/bin/env python3
# Copyright © 2014 Mattias Andrée (maandree@member.fsf.org)
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
import math
r_curve = [i / 255 for i in range(256)]
g_curve = [i / 255 for i in range(256)]
b_curve = [i / 255 for i in range(256)]
def curves(r, g, b):
'''
Generate a tuple of curve–parameter pairs
@param r The red parameter
@param g The green parameter
@param b The blue parameter
@return ((r_curve, r), (g_curve, g), (b_curve, b))
'''
return ((r_curve, r), (g_curve, g), (b_curve, b))
def sigmoid(r, g, b):
'''
Apply S-curve correction on the colour curves
@param r:float The sigmoid parameter for the red curve
@param g:float The sigmoid parameter for the green curve
@param b:float The sigmoid parameter for the blue curve
'''
for (curve, level) in curves(r, g, b):
if not level == 1.0:
for i in range(256):
try:
curve[i] = 0.5 - math.log(1 / curve[i] - 1) / level
except:
curve[i] = 0;
def contrast(r, g, b):
'''
Apply contrast correction on the colour curves
@param r:float The contrast parameter for the red curve
@param g:float The contrast parameter for the green curve
@param b:float The contrast parameter for the blue curve
'''
for (curve, level) in curves(r, g, b):
if not level == 1.0:
for i in range(256):
curve[i] = (curve[i] - 0.5) * level + 0.5
def brightness(r, g, b):
'''
Apply brightness correction on the colour curves
@param r:float The brightness parameter for the red curve
@param g:float The brightness parameter for the green curve
@param b:float The brightness parameter for the blue curve
'''
for (curve, level) in curves(r, g, b):
if not level == 1.0:
for i in range(256):
curve[i] *= level
def gamma(r, g, b):
'''
Apply gamma correction on the colour curves
@param r:float The gamma parameter for the red curve
@param g:float The gamma parameter for the green curve
@param b:float The gamma parameter for the blue curve
'''
for (curve, level) in curves(r, g, b):
if not level == 1.0:
for i in range(256):
curve[i] **= level
def clip():
'''
Clip all values belowed the actual minimum and above actual maximums
'''
for curve in (r_curve, g_curve, b_curve):
for i in range(256):
curve[i] = min(max(0.0, curve[i]), 1.0)
sigmoid(1.0, 1.0, 1.0)
clip()
contrast(1.0, 1.0, 1.0)
brightness(1.0, 1.0, 1.0)
gamma(1.0, 1.0, 1.0)
clip()
for curve in (r_curve, g_curve, b_curve):
for i in range(256):
curve[i] = int(curve[i] * 65535 + 0.5)
print(r_curve)
print(g_curve)
print(b_curve)
print(Math.e)
