Thumbnail crop

<?php
    /**
     * This classes allows you to create thumbnails. Input images will be resized,
     * while the ratio keeps intact, and will cropped to the size given.
     * @author Corné Dorrestijn
     * @license http://www.gnu.org/copyleft/lesser.html GNU Library General Public License
     * @package Default
     */
    class Thumbnail
    {
        private $imageData, $newImage, $sourceWidth, $sourceHeight;
        public  $width, $height;
        public $quality = 1;
        /**
         * Constructor
         * @param string $url The url to the local file.
         * @param integer $width The width of the thumbnail, default 100px.
         * @param integer $height The height of the thumbnail, default 100px.
         * @return void|String returns a string if there is a error.
         */
        public function __construct($url, $width = 100, $height = 100)
        {
            if(!isset($url) && $url === undefined && $url === '') return "No image url given.";
            if(!is_readable($url)) return 'Image "' . $url . '" file not readable.';
            $this->width = $width;
            $this->height = $height;
            $this->imageData = imagecreatefromstring(file_get_contents($url));
            list($this->sourceWidth, $this->sourceHeight) = getimagesize($url);
            $this->redraw();
            return;
        }

        /**
         * Generates a jpeg image.
         * @param boolean $redraw If set to true it will redraw the image.
         * @param string $path If set it will save the image to the given path.
         * @return void|String returns a string if there is a error.
         */
        public function getJpeg($redraw = true, $path = '')
        {
            if($redraw) $this->redraw();
            $q = round($this->quality * 99);
            if($path !== '')
            {
                if(imagejpeg($this->newImage, $path, $q))
                {

                }
                else
                {
                    return "Image NOT saved";
                }
            }
            else
            {
                header ('Content-Type: image/jpeg');
                imagejpeg($this->newImage, NULL, $q);
            }

            imagedestroy($this->newImage);
            return;
        }

        /**
         * Generates a png image.
         * @param boolean $redraw If set to true it will redraw the image.
         * @param string $path If set it will save the image to the given path.
         * @return void|String returns a string if there is a error.
         */
        public function getPng($redraw = true, $path = '')
        {
            if($redraw) $this->redraw();
            $q = 9-round($this->quality * 9);
            if($path !== '')
            {
                if(imagepng($this->newImage, $path, $q))
                {

                }
                else
                {
                    return "Image NOT saved";
                }
            }
            else
            {
                header ('Content-Type: image/png');
                imagepng($this->newImage, NULL, $q);
            }

            imagedestroy($this->newImage);
            return;
        }

        /**
         * Generates a gif image.
         * @param boolean $redraw If set to true it will redraw the image.
         * @param string $path If set it will save the image to the given path.
         * @return void|String returns a string if there is a error.
         */
        public function getGif($redraw = true, $path = '')
        {
            if($redraw) $this->redraw();
            if($path !== '')
            {
                if(imagegif($this->newImage, $path))
                {

                }
                else
                {
                    return "Image NOT saved";
                }
            }
            else
            {
                header ('Content-Type: image/gif');
                imagegif($this->newImage);
            }
            imagedestroy($this->newImage);
            return;
        }

        /**
         * Draws the scaled and cropped image in $this->newImage.
         * @return void.
         */
        private function redraw()
        {
            $newWidth = $this->width;
            $newHeight = $this->height;
            $offsetX = 0;
            $offsetY = 0;
            $pr = $this->sourceWidth/$this->sourceHeight;
            $tr = $this->width/$this->height;
            if($pr > $tr)
            {
                $newWidth = round($this->height*$pr);
                $offsetX = -round(($newWidth - $this->width) / 2);
            }
            else
            {
                $newHeight = round($this->width/$pr);
                $offsetY = -round(($newHeight - $this->height) / 2);
            }
            $this->newImage = imagecreatetruecolor($this->width, $this->height);
            imagecopyresampled($this->newImage, $this->imageData, $offsetX, $offsetY, 0, 0, $newWidth, $newHeight, $this->sourceWidth, $this->sourceHeight);
            return;
        }
    }
?>