diff options
Diffstat (limited to 'src/blackbody.py')
| -rw-r--r-- | src/blackbody.py | 175 |
1 files changed, 98 insertions, 77 deletions
diff --git a/src/blackbody.py b/src/blackbody.py index 41c6fe5..02972da 100644 --- a/src/blackbody.py +++ b/src/blackbody.py @@ -18,6 +18,7 @@ # This module implements support for colour temperature based # calculation of white points +import os import math from colour import * @@ -38,13 +39,17 @@ def series_d(temperature): @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 ''' - x = 0 - ks = ((0.244063, 0), (0.09911, 1), (2.9678, 2), (-4.6070, 3)) + # Get coefficients for calculating the x component + # of the colour in the CIE xyY colour space + x, ks = 0, (0.244063, 0.09911, 2.9678, -4.6070) if temperature > 7000: - ks = ((0.237040, 0), (0.24748, 1), (1.9018, 2), (-2.0064, 3)) - for (k, d) in ks: + ks = (0.237040, 0.24748, 1.9018, -2.0064) + # Calculate the x component of the colour in the CIE xyY colour space + for d, k in enumerate(ks): x += k * 10 ** (d * 3) / temperature ** d + # Calculate the y component of the colour in the CIE xyY colour space y = 2.870 * x - 3.000 * x ** 2 - 0.275 + # Convert to sRGB and return, with full illumination return ciexyy_to_srgb(x, y, 1.0) @@ -55,18 +60,14 @@ def simple_whitepoint(temperature): @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 + r, g, b, temp = 1, 1, 1, temperature / 100 if temp > 66: - temp -= 60 - r = 1.292936186 * temp ** 0.1332047592 - g = 1.129890861 * temp ** -0.0755148492 + r = 1.292936186 * (temp - 60) ** 0.1332047592 + g = 1.129890861 * (temp - 60) ** -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 + if temp < 66: + b = 0 if temp <= 19 else 0.543206789 * math.log(temp - 10) - 1.196254089 return (r, g, b) @@ -75,30 +76,19 @@ def cmf_2deg(temperature): ''' Calculate the colour for a blackbody temperature using raw CIE 1931 2 degree CMF data with interpolation - Using `lambda t : divide_by_maximum(cmf_2deg(t))` as the algorithm is better than just `cmf_2deg` + Using `lambda t : divide_by_maximum(cmf_2deg(t))` as the algorithm is better than just `cmf_2deg`, + `lambda t : clip_whitepoint(divide_by_maximum(cmf_2deg(t)))` is even better if you plan to use really + low temperatures, @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 ''' global cmf_2deg_cache if cmf_2deg_cache is None: - with open(DATADIR + '/2deg', 'rb') as file: - cmf_2deg_cache = file.read() - cmf_2deg_cache = cmf_2deg_cache.decode('utf-8', 'error').split('\n') - cmf_2deg_cache = filter(lambda x : not x == '', cmf_2deg_cache) - cmf_2deg_cache = [[float(x) for x in x_y.split(' ')] for x_y in cmf_2deg_cache] - temp = min(max(1000, temperature), 40000) - x, y = 0, 0 - if (temp % 100) == 0: - (x, y) = cmf_2deg_cache[int((temp - 1000) // 100)] - else: - temp -= 1000 - (x1, y1) = cmf_2deg_cache[int(temp // 100)] - (x2, y2) = cmf_2deg_cache[int(temp // 100 + 1)] - temp = (temp % 100) / 100 - x = x1 * (1 - temp) + x2 * temp - y = y1 * (1 - temp) + y2 * temp - return ciexyy_to_srgb(x, y, 1.0) + # Load, parse and cache lookup table if not cached + cmf_2deg_cache = get_blackbody_lut('2deg') + # Calculate whitepoint + return cmf_xdeg(temperature, cmf_2deg_cache) cmf_10deg_cache = None @@ -106,30 +96,51 @@ def cmf_10deg(temperature): ''' Calculate the colour for a blackbody temperature using raw CIE 1964 10 degree CMF data with interpolation - Using `lambda t : divide_by_maximum(cmf_10deg(t))` as the algorithm is better than just `cmf_10deg` + Using `lambda t : divide_by_maximum(cmf_10deg(t))` as the algorithm is better than just `cmf_10deg`, + `lambda t : clip_whitepoint(divide_by_maximum(cmf_10deg(t)))` is even better if you plan to use really + low temperatures, @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 ''' global cmf_10deg_cache if cmf_10deg_cache is None: - with open(DATADIR + '/10deg', 'rb') as file: - cmf_10deg_cache = file.read() - cmf_10deg_cache = cmf_10deg_cache.decode('utf-8', 'error').split('\n') - cmf_10deg_cache = filter(lambda x : not x == '', cmf_10deg_cache) - cmf_10deg_cache = [[float(x) for x in x_y.split(' ')] for x_y in cmf_10deg_cache] - temp = min(max(1000, temperature), 40000) - x, y = 0, 0 - if (temp % 100) == 0: - (x, y) = cmf_10deg_cache[int((temp - 1000) // 100)] + # Load, parse and cache lookup table if not cached + cmf_10deg_cache = get_blackbody_lut('10deg') + # Calculate whitepoint + return cmf_xdeg(temperature, cmf_10deg_cache) + + +def cmf_xdeg(temperature, lut, temp_min = 1000, temp_max = 40000, temp_step = 100): + ''' + Calculate the colour for a blackbody temperature using + raw data in the CIE xyY colour space with interpolation + + This function is intended as help functions for the two functions above this one in this module + + @param temperature:float The blackbody temperature in kelvins + @param lut:list<[x:float, y:float]> Raw data lookup table + @param temp_min:float The lowest temperature in the lookup table + @param temp_max:float The highest temperature in the lookup table + @param temp_step:float The interval between the temperatures + @return :(r:float, g:float, b:float) The whitepoint in [0, 1] sRGB + ''' + # Clip temperature to definition domain and remove offset + x, y, temp = 0, 0, min(max(temp_min, temperature), temp_max) - temp_min + if temp % temp_step == 0: + # Exact temperature is included in the lookup table + (x, y) = lut[int(temp // temp_step)] else: - temp -= 1000 - (x1, y1) = cmf_10deg_cache[int(temp // 100)] - (x2, y2) = cmf_10deg_cache[int(temp // 100 + 1)] - temp = (temp % 100) / 100 - x = x1 * (1 - temp) + x2 * temp - y = y1 * (1 - temp) + y2 * temp - return ciexyy_to_srgb(x, y, 1) + # x component floor and y component floor + floor = lut[int(temp // temp_step)] + # x component ceiling and y component ceiling + celiing = lut[int(temp // temp_step + 1)] + # Weight + temp = (temp % temp_step) / temp_step + # Interpolation + (x, y) = [c1 * (1 - temp) + c2 * temp for c1, c2 in zip(floor, ceilng)] + # Convert to sRGB + return ciexyy_to_srgb(x, y, 1.0) redshift_cache, redshift_old_cache = None, None @@ -144,43 +155,55 @@ def redshift(temperature, old_version = False, linear_interpolation = False): @return :(float, float, float) The red, green and blue components of the white point ''' global redshift_cache, redshift_old_cache - cache = None - if not old_version: - if redshift_cache is None: - with open(DATADIR + '/redshift', 'rb') as file: - redshift_cache = file.read() - redshift_cache = redshift_cache.decode('utf-8', 'error').split('\n') - redshift_cache = filter(lambda x : not x == '', redshift_cache) - redshift_cache = [[float(x) for x in r_g_b.split(' ')] for r_g_b in redshift_cache] - cache = redshift_cache - else: - if redshift_old_cache is None: - with open(DATADIR + '/redshift_old', 'rb') as file: - redshift_old_cache = file.read() - redshift_old_cache = redshift_old_cache.decode('utf-8', 'error').split('\n') - redshift_old_cache = filter(lambda x : not x == '', redshift_old_cache) - redshift_old_cache = [[float(x) for x in r_g_b.split(' ')] for r_g_b in redshift_old_cache] - cache = redshift_old_cache - temp = min(max(1000, temperature), 10000 if old_version else 25100) + # Retrieve cache + cache = redshift_old_cache if old_version else redshift_cache + if cache is None: + # Load and parse lookup table if not cached + cache = get_blackbody_lut('redshift_old' if old_version else 'redshift') + # Cache lookup table + if old_version: redshift_old_cache = cache + else: redshift_cache = cache + # Clip to definition domain and remove offset + temp = min(max(1000, temperature), 10000 if old_version else 25100) - 1000 r, g, b = 1, 1, 1 if (temp % 100) == 0: - (r, g, b) = cache[int((temp - 1000) // 100)] + # Exact temperature is included in the lookup table + (r, g, b) = cache[int(temp // 100)] else: - temp -= 1000 - (r1, g1, b1) = cache[int(temp // 100)] - (r2, g2, b2) = cache[int(temp // 100 + 1)] + # Floor + rgb1 = cache[int(temp // 100)] + # Ceiling + rgb2 = cache[int(temp // 100 + 1)] + # Weight temp = (temp % 100) / 100 + # Interpolation if linear_interpolation: - (r, g, b) = standard_to_linear(r, g, b) - r = r1 * (1 - temp) + r2 * temp - g = g1 * (1 - temp) + g2 * temp - b = b1 * (1 - temp) + b2 * temp + (rgb1, rgb2) = [standard_to_linear(*rgb) for rgb in (rgb1, rgb2)] + (r, g, b) = [c1 * (1 - temp) + c2 * temp for c1, c2 in zip(rgb1, rgb2)] if linear_interpolation: (r, g, b) = linear_to_standard(r, g, b) return (r, g, b) +def get_blackbody_lut(filename): + ''' + Load and parse a blackbody data lookup table + + This function is intended as help functions for the functions above this one in this module + + @param filename:str The filename of the lookup table + @return :list<list<float>> A float matrix of all values in the lookup table + ''' + # Load lookup table + lut = None + with open(DATADIR + os.sep + filename, 'rb') as file: + lut = file.read().decode('utf-8', 'error').split('\n') + # Parse lookup table + return [[float(cell) for cell in line.split(' ')] for line in lut if not line == ''] + + + def divide_by_maximum(rgb): ''' Divide all colour components by the value of the most prominent colour component @@ -189,9 +212,7 @@ def divide_by_maximum(rgb): @return :[float, float, float] The three colour components divided by the maximum ''' m = max([abs(x) for x in rgb]) - if m != 0: - return [x / m for x in rgb] - return rgb + return rgb if m == 0 else [x / m for x in rgb] def clip_whitepoint(rgb): |