An extension for resampling SilverStripe images on upload.

ResampleUpload.php

<?php

/**
 * An extension to SilverStripes inbuilt {@link Image} class to handle resizing 
 * large images on upload either through the backend interface or through upload
 * forms.
 *
 * File is resized to a copy, then the original is deleted and the smaller image
 * moved back.
 *
 * Usage:
 *	<code>
 *	DataObject::add_extension('Image', 'ResampleUpload');
 *	</code>
 *
 * Options:
 * 	Configure the max size using either statics or through instance level 
 *	variables. Note that if using instance level then it won't apply on things
 * 	like admin panels.
 *
 *	<code>
 *	ResampleUpload::$default_max_x = 45;
 *	ResampleUpload::$default_max_y = 100;
 *	</code>
 *	
 *
 * @todo provide options to archive large images
 *
 * @author Will Rossiter <will@fullscreen.io>
 * @license http://sam.zoy.org/wtfpl/
 */
class ResampleUpload extends DataObjectDecorator {
	
	static $default_max_x = 1024;
	static $default_max_y = 1024;
	
	private $maxX, $maxY;
	
	function setMaxX($x) {
		$this->maxX = $x;
	}
	
	function setMaxY($y) {
		$this->maxY = $y;
	}
	
	function getMaxX() {
		return ($this->maxX) ? $this->maxX : self::$default_max_x;	
	}
	
	function getMaxY() {
		return ($this->maxY) ? $this->maxY : self::$default_max_y;	
	}
	
	function onAfterUpload() {
		$this->ensureFileIsSmall();
	}
	
	function onAfterWrite() {
		$this->ensureFileIsSmall();
	}
	
	function ensureFileIsSmall() {
		$extension = strtolower($this->owner->getExtension());
		
		if($this->owner->getHeight() > $this->getMaxX() || $this->owner->getWidth() > $this->getMaxY()) {
			$original = $this->owner->getFullPath();			
			$resampled = $original. '.tmp.'. $extension;

			$gd = new GD($original);

			if($gd->hasGD()) {
				$gd = $gd->resizeRatio($this->getMaxX(), $this->getMaxY());

				if($gd) {
					$gd->writeTo($resampled);
					unlink($original);
					rename($resampled, $original);
				}
			}
		}
	}
}