colour temperature

Signed-off-by: Mattias Andrée <maandree@operamail.com>

2 files changed, 246 insertions, 29 deletions

diff --git a/src/__main__.py b/src/__main__.py
index 722f879..92b8cdc 100755
--- a/src/__main__.py
+++ b/src/__main__.py
@@ -16,10 +16,20 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 import math
 
+from colour import *
 
-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)]
+
+DATADIR = '.'
+
+i_size = 2 ** 8
+o_size = 2 ** 16
+r_curve = [i / (i_size - 1) for i in range(i_size)]
+g_curve = [i / (i_size - 1) for i in range(i_size)]
+b_curve = [i / (i_size - 1) for i in range(i_size)]
+clip_result = True
+
+cmf_2deg_cache = None
+cmf_10deg_cache = None
 
 
 def curves(r, g, b):
@@ -34,26 +44,132 @@ def curves(r, g, b):
     return ((r_curve, r), (g_curve, g), (b_curve, b))
 
 
-def sigmoid(r, g, b):
+def series_d(temperature):
     '''
-    Apply S-curve correction on the colour curves
+    Calculate the colour for a blackbody temperature
     
-    @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
+    @param   temperature:float       The blackbody temperature in kelvins, must be inside [4000, 7000]
+    @return  :(float, float, float)  The red, green and blue components of the white point
     '''
-    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;
+    x = 0
+    ks = ((0.244063, 0), (0.09911, 1), (2.9678, 2), (-4.6070, 3))
+    if temperature > 7000:
+        ks = ((0.237040, 0), (0.24748, 1), (1.9018, 2), (-2.0064, 3))
+    for (k, d) in ks:
+        x += k * 10 ** (d * 3) / temperature ** d
+    y = 2.870 * x - 3.000 * x ** 2 - 0.275
+    return to_srgb(x, y, 1.0)
+
+def simple_whitepoint(temperature):
+    '''
+    Calculate the colour for a blackbody temperature using a simple, but inaccurate, algorithm
+    
+    @param   temperature:float       The blackbody temperature in kelvins, not guaranteed for values outside [1000, 40000]
+    @return  :(float, float, float)  The red, green and blue components of the white point
+    '''
+    r, g, b = 1, 1, 1
+    temp = temperature / 100
+    if temp > 66:
+        temp -= 60
+        r = 1.292936186 * temp ** 0.1332047592
+        g = 1.129890861 * temp ** -0.0755148492
+    else:
+        g = 0.390081579 * math.log(temp) - 0.631841444
+        if temp <= 19:
+            b = 0
+        elif temp < 66:
+            b = 0.543206789 * math.log(temp - 10) - 1.196254089
+    return (r, g, b)
+
+def cmf_2deg(temperature):
+    '''
+    Calculate the colour for a blackbody temperature using raw CIE 1931 2 degree CMF data with interpolation
+    
+    @param   temperature:float       The blackbody temperature in kelvins, clipped to [1000, 40000]
+    @return  :(float, float, float)  The red, green and blue components of the white point
+    '''
+    if cmf_2deg_cache is None:
+        with open(DATADIR + '/2deg', 'rb') as file:
+            cmf_2deg_cache = file.read()
+        cmf_2deg_cache.decode('utf-8', 'error').split('\n')
+        cmf_2deg_cache = [[float(x) for x in x_y.split(' ')] for x_y in cmf_2deg_cache]
+    temperature = min(max(0, temperature), 1000)
+    x, y = 0, 0
+    if (temp % 100) == 0:
+        (x, y) = temperature[(temp - 1000) // 100]
+    else:
+        temp -= 1000
+        (x1, y1) = temperature[temp // 100]
+        (x2, y2) = temperature[temp // 100 + 1]
+        temp = (temp % 100) / 100
+        x = x1 * temp + x2 * (1 - temp)
+        y = y1 * temp + y2 * (1 - temp)
+    return to_srgb(x, y, 1.0)
+
+def cmf_10deg(temperature):
+    '''
+    Calculate the colour for a blackbody temperature using raw CIE 1964 10 degree CMF data with interpolation
+    
+    @param   temperature:float       The blackbody temperature in kelvins, clipped to [1000, 40000]
+    @return  :(float, float, float)  The red, green and blue components of the white point
+    '''
+    if cmf_2deg_cache is None:
+        with open(DATADIR + '/10deg', 'rb') as file:
+            cmf_2deg_cache = file.read()
+        cmf_2deg_cache.decode('utf-8', 'error').split('\n')
+        cmf_2deg_cache = [[float(x) for x in x_y.split(' ')] for x_y in cmf_2deg_cache]
+    temperature = min(max(0, temperature), 1000)
+    x, y = 0, 0
+    if (temp % 100) == 0:
+        (x, y) = temperature[(temp - 1000) // 100]
+    else:
+        temp -= 1000
+        (x1, y1) = temperature[temp // 100]
+        (x2, y2) = temperature[temp // 100 + 1]
+        temp = (temp % 100) / 100
+        x = x1 * temp + x2 * (1 - temp)
+        y = y1 * temp + y2 * (1 - temp)
+    return to_srgb(x, y, 1.0)
+
+
+def temperature(temperature, algorithm, linear_rgb = True):
+    '''
+    Change colour temperature according to the CIE illuminant series D
+    
+    @param  temperature:float                        The blackbody temperature in kelvins
+    @param  algorithm:(float)→(float, float, float)  Algorithm for calculating a white point, for example `series_d` or `simple_whitepoint`
+    @param  linear_rgb:[bool]                        Whether to use linear RGB, otherwise sRG is used
+    '''
+    if temperature == 6500:
+        return
+    (r, g, b) = algorithm(temperature)
+    if linear_rgb:
+        for curve in (r_curve, g_curve, b_curve):
+            for i in range(i_size):
+                R, G, B = r_curve[i], g_curve[i], b_curve[i]
+                (R, G, B) = standard_to_linear(R, G, B)
+                r_curve[i], g_curve[i], b_curve[i] = R, G, B
+    rgb_brightness(r, g, b)
+    if linear_rgb:
+        for curve in (r_curve, g_curve, b_curve):
+            for i in range(i_size):
+                R, G, B = r_curve[i], g_curve[i], b_curve[i]
+                (R, G, B) = linear_to_standard(R, G, B)
+                r_curve[i], g_curve[i], b_curve[i] = R, G, B
 
+def divide_by_maximum():
+    '''
+    Divide all colour components by the value of the most prominent colour component for each colour
+    '''
+    for i in range(i_size):
+        m = max([abs(x) for x in (r_curve[i], g_curve[i], b_curve[i])])
+        if m != 0:
+            for curve in (r_curve, g_curve, b_curve):
+                curve[i] /= m
 
-def contrast(r, g, b):
+def rgb_contrast(r, g, b):
     '''
-    Apply contrast correction on the colour curves
+    Apply contrast correction on the colour curves using sRGB
     
     @param  r:float  The contrast parameter for the red curve
     @param  g:float  The contrast parameter for the green curve
@@ -61,12 +177,23 @@ def contrast(r, g, b):
     '''
     for (curve, level) in curves(r, g, b):
         if not level == 1.0:
-            for i in range(256):
+            for i in range(i_size):
                 curve[i] = (curve[i] - 0.5) * level + 0.5
 
-def brightness(r, g, b):
+def cie_contrast(level):
     '''
-    Apply brightness correction on the colour curves
+    Apply contrast correction on the colour curves using CIE XYZ
+    
+    @param  level:float  The brightness parameter
+    '''
+    if not level == 1.0:
+        for i in range(i_size):
+            (x, y, Y) = to_ciexyy(r_curve[i], g_curve[i], b_curve[i])
+            (r_curve[i], g_curve[i], b_curve[i]) = to_rgb(x, y, Y * level)
+
+def rgb_brightness(r, g, b):
+    '''
+    Apply brightness correction on the colour curves using sRGB
     
     @param  r:float  The brightness parameter for the red curve
     @param  g:float  The brightness parameter for the green curve
@@ -74,9 +201,20 @@ def brightness(r, g, b):
     '''
     for (curve, level) in curves(r, g, b):
         if not level == 1.0:
-            for i in range(256):
+            for i in range(i_size):
                 curve[i] *= level
 
+def cie_brightness(level):
+    '''
+    Apply brightness correction on the colour curves using CIE XYZ
+    
+    @param  level:float  The brightness parameter
+    '''
+    if not level == 1.0:
+        for i in range(i_size):
+            (x, y, Y) = to_ciexyy(r_curve[i], g_curve[i], b_curve[i])
+            (r_curve[i], g_curve[i], b_curve[i]) = to_rgb(x, y, Y * level)
+
 def gamma(r, g, b):
     '''
     Apply gamma correction on the colour curves
@@ -87,31 +225,54 @@ def gamma(r, g, b):
     '''
     for (curve, level) in curves(r, g, b):
         if not level == 1.0:
-            for i in range(256):
+            for i in range(i_size):
                 curve[i] **= level
+    
+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 level is not None:
+            for i in range(i_size):
+                try:
+                    curve[i] = 0.5 - math.log(1 / curve[i] - 1) / level
+                except:
+                    curve[i] = 0;
 
 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):
+        for i in range(i_size):
             curve[i] = min(max(0.0, curve[i]), 1.0)
 
 
-sigmoid(1.0, 1.0, 1.0)
+temperature(6500, series_d, True)
+divide_by_maximum()
+temperature(6500, simple_whitepoint, True)
 clip()
-contrast(1.0, 1.0, 1.0)
-brightness(1.0, 1.0, 1.0)
+rgb_contrast(1.0, 1.0, 1.0)
+cie_contrast(1.0)
+rgb_brightness(1.0, 1.0, 1.0)
+cie_brightness(1.0)
 gamma(1.0, 1.0, 1.0)
+sigmoid(None, None, None)
 clip()
 
 
 for curve in (r_curve, g_curve, b_curve):
-    for i in range(256):
-        curve[i] = int(curve[i] * 65535 + 0.5)
+    for i in range(i_size):
+        curve[i] = int(curve[i] * (o_size - 1) + 0.5)
+        if clip_result:
+            curve[i] = min(max(0, curve[i]), (o_size - 1))
 print(r_curve)
 print(g_curve)
 print(b_curve)
-print(Math.e)
+
 
diff --git a/src/colour.py b/src/colour.py
new file mode 100644
index 0000000..df5b38d
--- /dev/null
+++ b/src/colour.py
@@ -0,0 +1,56 @@
+#!/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/>.
+
+
+def linear_to_standard(*colour):
+    return [12.92 * c if c <= 0.0031308 else (1 + 0.055) * c ** (1 / 2.4) - 0.055 for c in colour]
+
+def standard_to_linear(*colour):
+    return [c / 12.92 if c <= 0.04045 else ((c + 0.055) / (1 + 0.055)) ** 2.4 for c in colour]
+
+def ciexyy_to_ciexyz(x, y, Y):
+    return [Y * x / y, Y, Y * (1 - x - y) / y]
+
+def ciexyz_to_ciexyy(X, Y, Z):
+    p = -Y / X
+    q = 1 + Y / X
+    y = 1 / (p / 2 + (p ** 2 / 4 - q) ** 0.5)
+    x = X * y / Y
+    return [x, y, Y]
+
+def ciexyz_to_linear(X, Y, Z):
+    r = 3.2406 * X - 1.5372 * Y - 0.4986 * Z
+    g = -0.9689 * X + 1.8758 * Y + 0.0415 * Z
+    b = 0.0557 * X - 0.2040 * Y + 1.0570 * Z
+    return [r, g, b]
+
+def linear_to_ciexyz(r, g, b):
+    X = 0.4124 * r + 0.3576 * g + 0.1805 * b
+    Y = 0.2126 * r + 0.7152 * g + 0.0722 * b
+    Z = 0.0193 * r + 0.1192 * g + 1.9502 * b
+    return [X, Y, Z]
+
+def to_ciexyy(r, g, b):
+    (r, g, b) = standard_to_linear(r, g, b)
+    (X, Y, Z) = linear_to_ciexyz(r, g, b)
+    return ciexyz_to_ciexyy(X, Y, Z)
+
+def to_srgb(x, y, Y):
+    (X, Y, Z) = ciexyy_to_ciexyz(x, y, Y)
+    (r, g, b) = ciexyz_to_linear(X, Y, Z)
+    return linear_to_standard(r, g, b)
+