Converting RGB (Red, Green, Blue) values to CMYK (Cyan, Magenta, Yellow, Key/Black) involves several steps. RGB is an additive color model (used for screens), while CMYK is a subtractive color model (used for printing).
Steps to Convert RGB to CMYK:
Normalize the RGB values:
Convert the RGB values (ranging from 0 to 255) to a range of 0 to 1 by dividing each value by 255.
r' = R / 255
g' = G / 255
b' = B / 255
Calculate the Key (Black, K): The Key (Black) component is calculated by finding the minimum value of the normalized RGB values:
K = 1 - max(r', g', b')
Calculate the Cyan, Magenta, and Yellow: Once you have the K value, you can calculate C, M, and Y as follows:
C = (1 - r' - K) / (1 - K)
M = (1 - g' - K) / (1 - K)
Y = (1 - b' - K) / (1 - K)
If K = 1, then C = M = Y = 0.
Adjust values:
If C, M, or Y results in a value less than 0, set it to 0.
CMYK Output:
The resulting C, M, Y, and K values will be in the range 0 to 1. You can optionally multiply each by 100 to convert them into percentages.
Example 1: RGB(255, 87, 51)
Normalize RGB:
r' = 255 / 255 = 1
g' = 87 / 255 ≈ 0.341
b' = 51 / 255 ≈ 0.2
Calculate Key (K):
K = 1 - max(1, 0.341, 0.2) = 1 - 1 = 0
Calculate Cyan (C), Magenta (M), and Yellow (Y):
C = (1 - 1 - 0) / (1 - 0) = 0 / 1 = 0
M = (1 - 0.341 - 0) / (1 - 0) = 0.659 / 1 = 0.659
Y = (1 - 0.2 - 0) / (1 - 0) = 0.8 / 1 = 0.8
CMYK = (0, 0.659, 0.8, 0) (or (0%, 66%, 80%, 0%))
Example 2: RGB(51, 204, 255)
Normalize RGB:
r' = 51 / 255 ≈ 0.2
g' = 204 / 255 ≈ 0.8
b' = 255 / 255 = 1
Calculate Key (K):
K = 1 - max(0.2, 0.8, 1) = 1 - 1 = 0
Calculate Cyan (C), Magenta (M), and Yellow (Y):
C = (1 - 0.2 - 0) / (1 - 0) = 0.8 / 1 = 0.8
M = (1 - 0.8 - 0) / (1 - 0) = 0.2 / 1 = 0.2
Y = (1 - 1 - 0) / (1 - 0) = 0 / 1 = 0
CMYK = (0.8, 0.2, 0, 0) (or (80%, 20%, 0%, 0%))
Example 3: RGB(128, 0, 128)
Normalize RGB:
r' = 128 / 255 ≈ 0.502
g' = 0 / 255 = 0
b' = 128 / 255 ≈ 0.502
Calculate Key (K):
K = 1 - max(0.502, 0, 0.502) = 1 - 0.502 = 0.498
Calculate Cyan (C), Magenta (M), and Yellow (Y):
C = (1 - 0.502 - 0.498) / (1 - 0.498) = 0 / 0.502 = 0
M = (1 - 0 - 0.498) / (1 - 0.498) = 0.502 / 0.502 = 1
Y = (1 - 0.502 - 0.498) / (1 - 0.498) = 0 / 0.502 = 0
CMYK = (0, 1, 0, 0.498) (or (0%, 100%, 0%, 50%))