RGB

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20 Sep 2026 - Nicola Asuni

Three additive channels, each a fraction between 0 and 1. Every hex code and colour name parses into this model, and every conversion passes through it: toCmykArray() on an Hsl object converts to RGB first.

Model

Item	Value
Type string	`RGB`
Enum case	`ColorModelType::Rgb`
Class	`\Com\Tecnick\Color\Model\Rgb`
PDF colour space	DeviceRGB
Notations	`#RGB`, `#RGBA`, `#RRGGBB`, `#RRGGBBAA`, colour names, `rgb()`, `rgba()`, `["RGB",r,g,b]`

Components

Component	Key	Range	Out of range
Red	`red`	0.0 to 1.0	clamped
Green	`green`	0.0 to 1.0	clamped
Blue	`blue`	0.0 to 1.0	clamped
Alpha	`alpha`	0.0 to 1.0, default 1.0	clamped

Construction

<?php

require_once __DIR__ . '/vendor/autoload.php';

$rgb = new \Com\Tecnick\Color\Model\Rgb([
    'red' => 0.2,
    'green' => 0.4,
    'blue' => 0.6,
]);

echo $rgb->getCssColor(), "\n";
echo $rgb->getRgbHexColor(), "\n";

rgb(51,102,153)
#336699

Output

Every accessor, against #336699:

Call	Result
`getCssColor()`	`rgb(51,102,153)`
`getRgbHexColor()`	`#336699`
`getRgbaHexColor()`	`#336699ff`
`getComponentsString()`	`0.200000 0.400000 0.600000`
`getPdfColor()`	`0.200000 0.400000 0.600000 rg`
`getPdfColor(true)`	`0.200000 0.400000 0.600000 RG`
`getJsPdfColor()`	`["RGB",0.200000,0.400000,0.600000]`
`getArray()`	`['R' => 0.2, 'G' => 0.4, 'B' => 0.6, 'A' => 1.0]`
`getNormalizedArray(255)`	`['R' => 51.0, 'G' => 102.0, 'B' => 153.0, 'A' => 1.0]`
`getPDFacArray()`	`[0.2, 0.4, 0.6]`

The Two Hex Getters

getRgbHexColor() drops the alpha channel, getRgbaHexColor() appends it. Both are on every model, not just this one.

$web = new \Com\Tecnick\Color\Web();

$col = $web->getColorObj('rgba(51,102,153,0.8)');

echo $col->getRgbHexColor(), "\n";
echo $col->getRgbaHexColor(), "\n";
echo $col->getCssColor(), "\n";

#336699
#336699cc
rgba(51,102,153,0.8)

Web::WEBHEX stores the eight-digit form, so a lookup in that constant and a call to getRgbHexColor() return strings of different lengths for the same colour. Compare through extractHexCode() or through the components, not by string equality.

Conversions

RGB reaches the other four models directly, and they reach each other through it. Conversions has the matrix and the formulas.