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RGBA Color Space

RGBA (Red, Green, Blue, Alpha) extends RGB with an alpha channel for transparency. It's commonly used in web graphics, UI design, and any application where transparency is needed.

Channels​

RGBA has four channels:

  • r (Red): Intensity of red light (0-255)
  • g (Green): Intensity of green light (0-255)
  • b (Blue): Intensity of blue light (0-255)
  • a (Alpha): Transparency/opacity (0-255)

Channel Ranges​

  • RGB channels (r, g, b): 0-255
  • Alpha channel (a): 0-255
    • 0 = fully transparent
    • 255 = fully opaque

Default Values​

  • RGB channels: Default to 0 (no color)
  • Alpha channel: Defaults to 255 (fully opaque)

This means an RGBA color with only RGB specified will be fully opaque.

Creating RGBA Colors​

use Negarity\Color\Color;

// Create an RGBA color with full opacity
$color = Color::rgba(255, 100, 50, 255);

// Create with 50% opacity
$semiTransparent = Color::rgba(255, 100, 50, 128);

// Create fully transparent
$transparent = Color::rgba(255, 100, 50, 0);

Working with RGBA Channels​

Getting Channel Values​

$color = Color::rgba(255, 128, 64, 200);

$r = $color->getR();  // 255
$g = $color->getG();  // 128
$b = $color->getB();  // 64
$a = $color->getA();  // 200

Checking Channel Existence​

use Negarity\Color\ColorSpace\RGBA;

RGBA::hasChannel('r');  // true
RGBA::hasChannel('g');  // true
RGBA::hasChannel('b');  // true
RGBA::hasChannel('a');  // true
RGBA::hasChannel('x');  // false

Getting Channel Defaults​

use Negarity\Color\ColorSpace\RGBA;

RGBA::getChannelDefaultValue('r');  // 0
RGBA::getChannelDefaultValue('g');  // 0
RGBA::getChannelDefaultValue('b');  // 0
RGBA::getChannelDefaultValue('a');  // 255 (fully opaque)

Getting All Channels​

use Negarity\Color\ColorSpace\RGBA;

RGBA::getChannels();  // ['r', 'g', 'b', 'a']

Validation​

RGBA automatically validates all channel values:

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

try {
    // This will throw InvalidColorValueException
    $color = Color::rgba(300, 100, 50, 128);  // R value exceeds 255
} catch (InvalidColorValueException $e) {
    // Handle error
}

try {
    // This will also throw InvalidColorValueException
    $color = Color::rgba(255, 100, 50, 300);  // Alpha value exceeds 255
} catch (InvalidColorValueException $e) {
    // Handle error
}

Use Cases​

  • Web Graphics: CSS rgba() colors, transparent backgrounds
  • UI Design: Overlays, shadows, glassmorphism effects
  • Image Editing: Layers with transparency
  • Game Development: Transparent sprites, UI elements
  • Data Visualization: Semi-transparent data points

Color Space Information​

use Negarity\Color\ColorSpace\RGBA;

RGBA::getName();  // "rgba"
RGBA::getChannels();  // ['r', 'g', 'b', 'a']
RGBA::supportsIlluminant();  // false
RGBA::supportsObserver();  // false

See Also​