Silverstripe Simple Image Size Upload Validator

ImageUpload_Validator.php

<?php

class ImageUpload_Validator extends Upload_Validator{

	public $minwidth;
	public $minheight;

	public function setMinDimensions($width,$height){
		if(is_numeric($width) && intval($width)>=0)
			$this->minwidth=intval($width);
		else
			user_error('Invalid minimum width, value must be numeric and at least 0',E_USER_ERROR);

		if(is_numeric($height) && intval($height)>=0)
			$this->minheight=intval($height);
		else
			user_error('Invalid minimum height, value must be numeric and at least 0',E_USER_ERROR);
	}

	public function isValidDimensions() {
		//if we cannot determine the image size return false
		if(!$dims = getimagesize($this->tmpFile['tmp_name']))
			return false;

		if(($this->minheight && $dims[1]<=$this->minheight) || ($this->minwidth && $dims[0]<=$this->minwidth))
			return false;

		return true;
	}

	public function validate(){
		if(!isset($this->tmpFile['name']) || empty($this->tmpFile['name']))
			return true;
		if(!$this->isValidDimensions()){
			$this->errors[]=sprintf('Minimum image size is %s x %s ', $this->minwidth?$this->minwidth.'px':'(ANY)',$this->minheight?$this->minheight.'px':'(ANY)');
			return false;
		}
		return parent::validate();
	}
}

MyObject.php

<?php

class MyObject extends DataObject{
	
	private static $has_one = array(
		'Image' => 'Image'
	);

	public function getCMSFields()
	{
		$fields = parent::getCMSFields();
	
		$uploadfield = new UploadField('Image','Main Image');
		
	    //setup the new validator
		$validator = new ImageUpload_Validator();
		$validator->setMinDimensions(1000,70);
		$validator->setAllowedExtensions(array('jpg','jpeg', 'gif', 'png'));
		$validator->setAllowedMaxFileSize(array('*' => 4194304));
		
		$uploadfield->setValidator($validator);
		$fields->addFieldToTab('Root.Main',$uploadfield,'Content');
		return $fields;
	}

}