Python/conversions/rgb_cmyk_conversion.py
Marek Mazij 6971af2416
feat: RGB to CMYK color converter ()
* feat: code functional, commented, tested

* fix: compering types, exception msg, line length

* fix: type hints
2023-10-23 18:22:09 -04:00

72 lines
2.0 KiB
Python

def rgb_to_cmyk(r_input: int, g_input: int, b_input: int) -> tuple[int, int, int, int]:
"""
Simple RGB to CMYK conversion. Returns percentages of CMYK paint.
https://www.programmingalgorithms.com/algorithm/rgb-to-cmyk/
Note: this is a very popular algorithm that converts colors linearly and gives
only approximate results. Actual preparation for printing requires advanced color
conversion considering the color profiles and parameters of the target device.
>>> rgb_to_cmyk(255, 200, "a")
Traceback (most recent call last):
...
ValueError: Expected int, found (<class 'int'>, <class 'int'>, <class 'str'>)
>>> rgb_to_cmyk(255, 255, 999)
Traceback (most recent call last):
...
ValueError: Expected int of the range 0..255
>>> rgb_to_cmyk(255, 255, 255) # white
(0, 0, 0, 0)
>>> rgb_to_cmyk(128, 128, 128) # gray
(0, 0, 0, 50)
>>> rgb_to_cmyk(0, 0, 0) # black
(0, 0, 0, 100)
>>> rgb_to_cmyk(255, 0, 0) # red
(0, 100, 100, 0)
>>> rgb_to_cmyk(0, 255, 0) # green
(100, 0, 100, 0)
>>> rgb_to_cmyk(0, 0, 255) # blue
(100, 100, 0, 0)
"""
if (
not isinstance(r_input, int)
or not isinstance(g_input, int)
or not isinstance(b_input, int)
):
msg = f"Expected int, found {type(r_input), type(g_input), type(b_input)}"
raise ValueError(msg)
if not 0 <= r_input < 256 or not 0 <= g_input < 256 or not 0 <= b_input < 256:
raise ValueError("Expected int of the range 0..255")
# changing range from 0..255 to 0..1
r = r_input / 255
g = g_input / 255
b = b_input / 255
k = 1 - max(r, g, b)
if k == 1: # pure black
return 0, 0, 0, 100
c = round(100 * (1 - r - k) / (1 - k))
m = round(100 * (1 - g - k) / (1 - k))
y = round(100 * (1 - b - k) / (1 - k))
k = round(100 * k)
return c, m, y, k
if __name__ == "__main__":
from doctest import testmod
testmod()