Image Resizing Class

    /**
     * Determines image type, calculates scaled image size, and returns resized image. If no width or height is
     * specified for the new image, the dimensions of the original image will be used, resulting in a copy
     * of the original image.
     *
     * @param string $original absolute path to original image file
     * @param string $new_filename absolute path to new image file to be created
     * @param integer $new_width (optional) width to scale new image (default 0)
     * @param integer $new_height (optional) height to scale image (default 0)
     * @param integer $quality quality of new image (default 100, resizePng will recalculate this value)
     *
     * @access public
     *
     * @return returns new image on success, false on failure. use ImageComponent::getErrors() to get an array
     * of errors on failure
     */
    public function resize($original, $new_filename, $new_width = 0, $new_height = 0, $quality = 100) {
        if(!($image_params = getimagesize($original))) {
            $this->__errors[] = 'Original file is not a valid image: ' . $orignal;
            return false;
        }
       
        $width = $image_params[0];
        $height = $image_params[1];
       
        if(0 != $new_width && 0 == $new_height) {
            $scaled_width = $new_width;
            $scaled_height = floor($new_width * $height / $width);
        } elseif(0 != $new_height && 0 == $new_width) {
            $scaled_height = $new_height;
            $scaled_width = floor($new_height * $width / $height);
        } elseif(0 == $new_width && 0 == $new_height) { //assume we want to create a new image the same exact size
            $scaled_width = $width;
            $scaled_height = $height;
        } else { //assume we want to create an image with these exact dimensions, most likely resulting in distortion
            $scaled_width = $new_width;
            $scaled_height = $new_height;
        }

        //create image       
        $ext = $image_params[2];
        switch($ext) {
            case IMAGETYPE_GIF:
                $return = $this->__resizeGif($original, $new_filename, $scaled_width, $scaled_height, $width, $height, $quality);
                break;
            case IMAGETYPE_JPEG:
                $return = $this->__resizeJpeg($original, $new_filename, $scaled_width, $scaled_height, $width, $height, $quality);
                break;
            case IMAGETYPE_PNG:
                $return = $this->__resizePng($original, $new_filename, $scaled_width, $scaled_height, $width, $height, $quality);
                break;   
            default:
                $return = $this->__resizeJpeg($original, $new_filename, $scaled_width, $scaled_height, $width, $height, $quality);
                break;
        }
       
        return $return;
    }
   
    public function getErrors() {
        return $this->__errors;
    }
   
    private function __resizeGif($original, $new_filename, $scaled_width, $scaled_height, $width, $height) {
        $error = false;
       
        if(!($src = imagecreatefromgif($original))) {
            $this->__errors[] = 'There was an error creating your resized image (gif).';
            $error = true;
        }
       
        if(!($tmp = imagecreatetruecolor($scaled_width, $scaled_height))) {
            $this->__errors[] = 'There was an error creating your true color image (gif).';
            $error = true;
        }
       
        if(!imagecopyresampled($tmp, $src, 0, 0, 0, 0, $scaled_width, $scaled_height, $width, $height)) {
            $this->__errors[] = 'There was an error creating your true color image (gif).';
            $error = true;
        }

        if(!($new_image = imagegif($tmp, $new_filename))) {
            $this->__errors[] = 'There was an error writing your image to file (gif).';
            $error = true;
        }
       
        imagedestroy($tmp);

        if(false == $error) {
            return $new_image;
        }
       
        return false;
    }
   
    private function __resizeJpeg($original, $new_filename, $scaled_width, $scaled_height, $width, $height, $quality) {
        $error = false;
       
        if(!($src = imagecreatefromjpeg($original))) {
            $this->__errors[] = 'There was an error creating your resized image (jpg).';
            $error = true;
        }

        if(!($tmp = imagecreatetruecolor($scaled_width, $scaled_height))) {
            $this->__errors[] = 'There was an error creating your true color image (jpg).';
            $error = true;
        }
       
        if(!imagecopyresampled($tmp, $src, 0, 0, 0, 0, $scaled_width, $scaled_height, $width, $height)) {
            $this->__errors[] = 'There was an error creating your true color image (jpg).';
            $error = true;
        }

        if(!($new_image = imagejpeg($tmp, $new_filename, $quality))) {
            $this->__errors[] = 'There was an error writing your image to file (jpg).';
            $error = true;
        }
       
        imagedestroy($tmp);
       
        if(false == $error) {
            return $new_image;
        }
       
        return false;
    }
   
    private function __resizePng($original, $new_filename, $scaled_width, $scaled_height, $width, $height, $quality) {
        $error = false;
        /**
         * we need to recalculate the quality for imagepng()
         * the quality parameter in imagepng() is actually the compression level,
         * so the higher the value (0-9), the lower the quality. this is pretty much
         * the opposite of how imagejpeg() works.
         */
        $quality = ceil($quality / 10); // 0 - 100 value
        if(0 == $quality) {
            $quality = 9;
        } else {
            $quality = ($quality - 1) % 9;
        }