/**
* {@inheritdoc}
*/
protected function doApply(CanvasInterface $canvas)
{
$c1 = clone $this->getFirstColor();
$c2 = clone $this->getSecondColor();
$line = new Line();
$width = $canvas->getWidth();
$height = $canvas->getHeight();
for ($i = 0; $i < $this->getWidth(); $i++) {
$alpha = round($i / $this->getWidth() * 127);
$c1->setAlpha($alpha);
$c2->setAlpha($alpha);
$line->setStart(new Coordinate($i, $i + 1))->setEnd(new Coordinate($i, $height - $i - 1))->setColor($c1)->draw($canvas)->setStart(new Coordinate($i, $i))->setEnd(new Coordinate($width - $i, $i))->draw($canvas)->setStart(new Coordinate($width - $i, $height - $i - 1))->setEnd(new Coordinate($width - $i, $i + 1))->setColor($c2)->draw($canvas)->setStart(new Coordinate($width - $i, $height - $i - 1))->setEnd(new Coordinate($i, $height - $i))->draw($canvas);
}
}
