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CMYK Color Space

CMYK (Cyan, Magenta, Yellow, Key/Black) is a subtractive color model used primarily in professional printing. Unlike RGB which is additive (adding light), CMYK is subtractive (subtracting light by adding ink).

Channels​

CMYK has four channels:

  • c (Cyan): Amount of cyan ink
  • m (Magenta): Amount of magenta ink
  • y (Yellow): Amount of yellow ink
  • k (Key/Black): Amount of black ink

Channel Ranges​

All channels have the same range:

  • Minimum: 0 (no ink)
  • Maximum: 100 (full ink coverage)

Values are typically expressed as percentages (0-100%).

Default Values​

All channels default to 0 when not specified, resulting in white (cmyk(0, 0, 0, 0)), which represents no ink on white paper.

Creating CMYK Colors​

use Negarity\Color\Color;

// Create a CMYK color
$color = Color::cmyk(0, 50, 100, 0);

// Pure cyan
$cyan = Color::cmyk(100, 0, 0, 0);

// Rich black (using all inks)
$richBlack = Color::cmyk(0, 0, 0, 100);

Working with CMYK Channels​

Getting Channel Values​

$color = Color::cmyk(25, 50, 75, 10);

$c = $color->getC();  // 25
$m = $color->getM();  // 50
$y = $color->getY();  // 75
$k = $color->getK();  // 10

Checking Channel Existence​

use Negarity\Color\ColorSpace\CMYK;

CMYK::hasChannel('c');  // true
CMYK::hasChannel('m');  // true
CMYK::hasChannel('y');  // true
CMYK::hasChannel('k');  // true
CMYK::hasChannel('r');  // false (that's RGB)

Getting Channel Defaults​

use Negarity\Color\ColorSpace\CMYK;

CMYK::getChannelDefaultValue('c');  // 0
CMYK::getChannelDefaultValue('m');  // 0
CMYK::getChannelDefaultValue('y');  // 0
CMYK::getChannelDefaultValue('k');  // 0

Getting All Channels​

use Negarity\Color\ColorSpace\CMYK;

CMYK::getChannels();  // ['c', 'm', 'y', 'k']

Validation​

CMYK automatically validates channel values:

use Negarity\Color\Color;
use Negarity\Color\Exception\InvalidColorValueException;

try {
    // This will throw InvalidColorValueException
    $color = Color::cmyk(150, 50, 100, 0);  // Cyan exceeds 100
} catch (InvalidColorValueException $e) {
    // Handle error
}

Understanding CMYK​

Subtractive Color Model​

CMYK is subtractive because:

  • Adding ink = Subtracting light
  • More ink = darker color
  • Less ink = lighter color
  • White = no ink (paper shows through)
  • Black = all inks (or just K for efficiency)

The K Channel (Key/Black)​

The black channel serves two purposes:

  1. Richer blacks: Pure black (K=100) is deeper than mixing CMY
  2. Cost efficiency: Using black ink is cheaper than mixing cyan, magenta, and yellow

Color Mixing​

  • Cyan + Magenta = Blue
  • Magenta + Yellow = Red
  • Yellow + Cyan = Green
  • Cyan + Magenta + Yellow = Dark brown/black (but K is preferred)

Use Cases​

  • Professional Printing: Offset printing, digital printing
  • Print Design: Preparing designs for print media
  • Brand Colors: Many brand colors are defined in CMYK
  • Color Matching: Matching screen colors to printed output
  • Prepress: Preparing files for commercial printing

Color Space Information​

use Negarity\Color\ColorSpace\CMYK;

CMYK::getName();  // "cmyk"
CMYK::getChannels();  // ['c', 'm', 'y', 'k']
CMYK::supportsIlluminant();  // false
CMYK::supportsObserver();  // false

See Also​