RGB to Color Temperature

and vice versa with a Python script

For a science project I had to convert a lot of JPG files to different color temperature output files. What I basically wanted was: a folder containing the same image in different color temperature nuances which were also named with the respective Kelvin value. I did some own calculations (thanks to Hernández 1999 at this point!) but came basically to almost the same values like Mitchell Charity in 2001. For all the copycats here: Below you find the values as a convenient python dictionary. Simply copy and paste the thing!

The values as a python dictionary

kelvin_table = { 1000: (255, 56, 0), 1100: (255, 71, 0), 1200: (255, 83, 0), 1300: (255, 93, 0), 1400: (255, 101, 0), 1500: (255, 109, 0), 1600: (255, 115, 0), 1700: (255, 121, 0), 1800: (255, 126, 0), 1900: (255, 131, 0), 2000: (255, 138, 18), 2100: (255, 142, 33), 2200: (255, 147, 44), 2300: (255, 152, 54), 2400: (255, 157, 63), 2500: (255, 161, 72), 2600: (255, 165, 79), 2700: (255, 169, 87), 2800: (255, 173, 94), 2900: (255, 177, 101), 3000: (255, 180, 107), 3100: (255, 184, 114), 3200: (255, 187, 120), 3300: (255, 190, 126), 3400: (255, 193, 132), 3500: (255, 196, 137), 3600: (255, 199, 143), 3700: (255, 201, 148), 3800: (255, 204, 153), 3900: (255, 206, 159), 4000: (255, 209, 163), 4100: (255, 211, 168), 4200: (255, 213, 173), 4300: (255, 215, 177), 4400: (255, 217, 182), 4500: (255, 219, 186), 4600: (255, 221, 190), 4700: (255, 223, 194), 4800: (255, 225, 198), 4900: (255, 227, 202), 5000: (255, 228, 206), 5100: (255, 230, 210), 5200: (255, 232, 213), 5300: (255, 233, 217), 5400: (255, 235, 220), 5500: (255, 236, 224), 5600: (255, 238, 227), 5700: (255, 239, 230), 5800: (255, 240, 233), 5900: (255, 242, 236), 6000: (255, 243, 239), 6100: (255, 244, 242), 6200: (255, 245, 245), 6300: (255, 246, 247), 6400: (255, 248, 251), 6500: (255, 249, 253), 6600: (254, 249, 255), 6700: (252, 247, 255), 6800: (249, 246, 255), 6900: (247, 245, 255), 7000: (245, 243, 255), 7100: (243, 242, 255), 7200: (240, 241, 255), 7300: (239, 240, 255), 7400: (237, 239, 255), 7500: (235, 238, 255), 7600: (233, 237, 255), 7700: (231, 236, 255), 7800: (230, 235, 255), 7900: (228, 234, 255), 8000: (227, 233, 255), 8100: (225, 232, 255), 8200: (224, 231, 255), 8300: (222, 230, 255), 8400: (221, 230, 255), 8500: (220, 229, 255), 8600: (218, 229, 255), 8700: (217, 227, 255), 8800: (216, 227, 255), 8900: (215, 226, 255), 9000: (214, 225, 255), 9100: (212, 225, 255), 9200: (211, 224, 255), 9300: (210, 223, 255), 9400: (209, 223, 255), 9500: (208, 222, 255), 9600: (207, 221, 255), 9700: (207, 221, 255), 9800: (206, 220, 255), 9900: (205, 220, 255), 10000: (207, 218, 255), 10100: (207, 218, 255), 10200: (206, 217, 255), 10300: (205, 217, 255), 10400: (204, 216, 255), 10500: (204, 216, 255), 10600: (203, 215, 255), 10700: (202, 215, 255), 10800: (202, 214, 255), 10900: (201, 214, 255), 11000: (200, 213, 255), 11100: (200, 213, 255), 11200: (199, 212, 255), 11300: (198, 212, 255), 11400: (198, 212, 255), 11500: (197, 211, 255), 11600: (197, 211, 255), 11700: (197, 210, 255), 11800: (196, 210, 255), 11900: (195, 210, 255), 12000: (195, 209, 255)}

The Python processing code

All the color transformations were done with a python matrix. After that the image was saved using the PIL library as JPG with the recpective Kelvin value as file name. I am aware that the progressive=False tag will be ignored although I observed that the images get a little larger when this tag is removed. (Don't ask me why.)
The code is absolutely NOT beautiful, but it does what it has to do.

from PIL import Image image_path = input("Path: ") image_save_path = input("Image save path: ") image = Image.open(image_path) file_type = '.jpg'

Insert here the kelvin _table from above!

kelvin_list = [1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, 3100, 3200, 3300, 3400, 3500, 3600, 3700, 3800, 3900, 4000, 4100, 4200, 4300, 4400, 4500, 4600, 4700, 4800, 4900, 5000, 5100, 5200, 5300, 5400, 5500, 5600, 5700, 5800, 5900, 6000, 6100, 6200, 6300, 6400, 6500, 6600, 6700, 6800, 6900, 7000, 7100, 7200, 7300, 7400, 7500, 7600, 7700, 7800, 7900, 8000, 8100, 8200, 8300, 8400, 8500, 8600, 8700, 8800, 8900, 9000, 9100, 9200, 9300, 9400, 9500, 9600, 9700, 9800, 9900, 10000, 10100, 10200, 10300, 10400, 10500, 10600, 10700, 10800, 10900, 11000, 11100, 11200, 11300, 11400, 11500, 11600, 11700, 11800, 11900, 12000] quality_factor = 2 # higher values means lesser quality. because. for i in range(0, len(kelvin_list), quality_factor): kelvin_value = kelvin_list[i] print('Working on Kelvin value: ', kelvin_value) temp = kelvin_table[kelvin_value] r, g, b = temp color_matrix = (r / 255.0, 0.0, 0.0, 0.0, 0.0, g / 255.0, 0.0, 0.0, 0.0, 0.0, b / 255.0, 0.0) new_image = image.convert('RGB', color_matrix) kelvin_list_string = str(kelvin_list[i]) seq = image_save_path + kelvin_list_string + file_type new_image.save(seq, "JPEG", quality=80, optimize=True, progressive=False) print('Saving Image: ', seq)

The output

Color temperature comparison kelvin