Scales

Scales lays half ellipses in rows, each row moved half a width against the one above, so the arcs overlap the way scales do. Take it for water, a roof, or any surface that should read as layered.

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';

$scales = Pattern::scales(width: 18, height: 12, thickness: 1);

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

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

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

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

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

Options

Pattern::scales() takes three measurements in user units. Style applies afterwards, and each call returns a new tile.

Setting	Default	Effect
`width`	`18`	span of one arc, and the width of the tile
`height`	`12`	rise of one arc, and the distance between two rows
`thickness`	`1`	line width, at most the height
`withColor(string)`	`currentColor`	stroke of the arcs; they are outlined, never filled
`withOpacity(?float)`	none	opacity of the tile, applied to the whole drawing at once, so an arc crossing another keeps one flat tone
`withAngle(float)`	`0`	turns the rows; at `180` the arcs open upwards
`withId(string)`	derived	fixes the identifier instead of deriving it from the tile content

A thickness above the height throws InvalidArgumentException.

How the tile closes

Rows sit one height apart and move half a width from one row to the next, so an arc apex lands on the junction of the two arcs above it. The offset only cancels after two rows, which is why the tile is width by 2 * height.

The aligned row crosses the middle of the tile, from one vertical edge to the other, so its two ends complete each other across the seam.

The shifted row straddles the horizontal edges, so it is drawn twice: once at 0.5 * height and once at 2.5 * height, one full period apart. Each of those is two arcs, one starting half a width to the left of the tile and one half a width inside it, so the piece cut off at one vertical edge comes back at the other.