GD Library Resize PHP

gdResize.php

function gdResize($uploadDir, $filename,$ext, $newWidth, $newHeight)
    {
        list($orginalWidth, $orginalHeight) = getimagesize($uploadDir. $filename . '.' . $ext);

        $ratio = $orginalWidth/$orginalHeight;

        if ($orginalWidth < $newWidth || $orginalHeight < $newHeight)
        {
            return  '';
        }
        else if ($newWidth/$newHeight > $ratio)
        {
            $newWidth = $newHeight * $ratio;
        }
        else
        {
            $newHeight = $newWidth / $ratio;
        }

        $thumb = imagecreatetruecolor($newWidth, $newHeight);

        $sourceFile = $uploadDir. $filename . '.'. $ext;
        switch ($ext)
        {
            case 'jpg':
                $source = imagecreatefromjpeg($sourceFile);
                break;
            case 'gif' :
                $source = imagecreatefromgif($sourceFile);
                break;
            case 'png' :
                imagealphablending($thumb, false);
                imagesavealpha($thumb, true);
                $transparency = imagecolorallocatealpha($thumb, 0, 0, 0, 127);
                imagefilledrectangle($thumb, 0, 0, $newWidth, $newHeight, $transparency);
                $source = imagecreatefrompng($sourceFile);
                break;
            case 'bmp' :
                $source = imagecreatefromwbmp($sourceFile);
                break;
        }

        imagecopyresized($thumb, $source, 0, 0, 0, 0, $newWidth, $newHeight, $orginalWidth, $orginalHeight);

        $thumbnailFile =  'thumb_' . $filename . '.' . $ext;

        switch ($ext)
        {
            case 'jpg':
                imagejpeg($thumb, $uploadDir .$thumbnailFile, 0);
                break;
            case 'gif' :
                imagegif($thumb, $uploadDir .$thumbnailFile, 0);
                break;
            case 'png' :

                imagepng($thumb, $uploadDir .$thumbnailFile, 0);
                break;
            case 'bmp' :
                imagewbmp($thumb, $uploadDir .$thumbnailFile, 0);
                break;
        }

        return $thumbnailFile;
    }