SilverStripe Imagick high quality and low file size

FixedImagickBackend.php

<?php
// smart defaults for high quality and low file size
// https://github.com/nwtn/php-respimg/blob/master/src/Respimg.php#L235
//	---
//	Only:
//	  classexists: 'Imagick'
//	---
//	Image:
//	  backend: 'FixedImagickBackend'
//	ImagickBackend:
//	  default_quality: 80
if(class_exists('Imagick')) {
	class FixedImagickBackend extends ImagickBackend
	{
		public function smartResize($columns, $rows, $optim = false) {
			$quality = 76;
			if ($qualityFromConfig = Config::inst()->get('ImagickBackend','default_quality')) {
				$quality = $qualityFromConfig;
			}

			$this->setOption('filter:support', '2.0');
			$this->thumbnailImage($columns, $rows, false, false, \Imagick::FILTER_TRIANGLE);
			if ($optim) {
				$this->unsharpMaskImage(0.25, 0.08, 8.3, 0.045);
			} else {
				$this->unsharpMaskImage(0.25, 0.25, 8, 0.065);
			}
			$this->posterizeImage(136, false);
			$this->setImageCompressionQuality($quality);
			$this->setOption('jpeg:fancy-upsampling', 'off');
			$this->setOption('png:compression-filter', '5');
			$this->setOption('png:compression-level', '9');
			$this->setOption('png:compression-strategy', '1');
			$this->setOption('png:exclude-chunk', 'all');
			$this->setInterlaceScheme(\Imagick::INTERLACE_NO);
			$this->setColorspace(\Imagick::COLORSPACE_SRGB);
			if (!$optim) {
				$this->stripImage();
			}
		}
		public function resize($width, $height) {
			if(!$this->valid()) return;

			if($width < 0 || $height < 0) throw new InvalidArgumentException("Image resizing dimensions cannot be negative");
			if(!$width && !$height) throw new InvalidArgumentException("No dimensions given when resizing image");
			if(!$width) throw new InvalidArgumentException("Width not given when resizing image");
			if(!$height) throw new InvalidArgumentException("Height not given when resizing image");

			//use whole numbers, ensuring that size is at least 1x1
			$width = max(1, round($width));
			$height = max(1, round($height));

			$geometry = $this->getImageGeometry();

			// Check that a resize is actually necessary.
			if ($width == $geometry["width"] && $height == $geometry["height"]) {
				return $this;
			}

			$new = clone $this;

			$new->smartResize($width, $height, 1, false);

			return $new;
		}
	}
}