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()