Checker

Checker alternates filled and empty cells. Only half the surface is painted: the other half carries no shape at all, so whatever sits underneath shows through it. Take it for a transparency ground, a board, or any two-tone surface where the second tone is the page itself.

Example

<?php

declare(strict_types=1);

use Atelier\Pattern\Pattern;
use Atelier\Pattern\PatternRegistry;
use Atelier\Svg\Document;
use Atelier\Svg\Dumper\CompactXmlDumper;
use Atelier\Svg\Element\Shape\RectElement;

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

$checker = Pattern::checker(size: 12);

$document = Document::create(360, 200);

(new PatternRegistry($checker))->attachTo($document);

$surface = new RectElement();
$surface->setX('0')->setY('0')->setWidth('360')->setHeight('200');
$surface->setAttribute('fill', $checker->fill());

$document->getRootElement()?->appendChild($surface);

echo (new CompactXmlDumper())->dump($document);

Options

Pattern::checker() takes one measurement in user units. Style applies afterwards, and each call returns a new tile.

Setting	Default	Effect
`size`	`12`	side of one cell; the tile is twice that on both axes
`withColor(string)`	`currentColor`	paint of the filled cells; the empty ones stay transparent
`withOpacity(?float)`	none	opacity of the tile; at a value below `1` the filled cells tint the surface instead of covering it
`withAngle(float)`	`0`	turns the board through `patternTransform`
`withId(string)`	derived	fixes the identifier instead of deriving it from the tile content

There is no thickness and no second colour: the pattern is the two filled cells, and the rest is the surface. size must be a finite number greater than zero, and nothing else is checked, because nothing else can fail to tile.

How the tile closes

A checkerboard only comes back to itself after two cells, so the tile spans 2 * size on both axes.

Two squares are drawn into it, at (0, 0) and (size, size). Both sit entirely inside the tile, meeting the boundary without crossing it, so nothing is drawn twice.

The two remaining cells hold no shape. They are not painted with a background colour, they are empty, which is what lets the surface underneath read through them.