class Image{
    //路径
    protected $path;
    //是否启用随机名字
    protected $isRandName;
    //要保存的图像类型
    protected $type;

    //通过构造方法队成员属性进行初始化
    function __construct($path=‘./‘,$isRandName=true,$type=‘png‘){
        $this->path = $path;
        $this->isRandName = $isRandName;
        $this->type = $type;
    }
    //对外公开的水印方法

    /**
     * @param char $image  原图
     * @param char $water  水印图片
     * @param char $postion 位置
     * @param int $tmp   透明度
     * @param char $prefix 前缀
     */
    function water($image,$water,$postion,$tmp=100,$prefix=‘water_‘){
        //判断这两个图片是否存在
        if(!file_exists($image)||!file_exists($water)){
            die(‘图片资源不存在‘);
        }
        //得到原图和水印图片的宽高
        $imageInfo = self::getImageInfo($image);
        $waterInfo = self::getImageInfo($water);
        //判断水印图片是否能贴上来
        if (!$this->checkImage($imageInfo,$waterInfo)){
            die(‘水印图片太大‘);
        }
        //打开图片
        $imageRes = self::openAnyImage($image);
        $waterRes = self::openAnyImage($water);
        //根据水印图片的位置计算水印图片的坐标
        $pos = $this->getPosition($postion,$imageInfo,$waterInfo);
        //将水印图片贴过来
        imagecopymerge($imageRes, $waterRes, $pos[‘x‘], $pos[‘y‘], 0, 0, $waterInfo["width"], $waterInfo["height"], $tmp);
        //得到要保存图片的文件名
        $newName = $this->createNewName($image,$prefix);
        //得到保存图片的路径,也就是文件的全路径
        $newPath = rtrim($this->path,‘/‘).‘/‘.$newName;
        //保存图片
        $this->saveImage($imageRes,$newPath);
        //销毁资源
        imagedestroy($imageRes);
        imagedestroy($waterRes);

        //返回路径
        return $newPath;
    }
    //保存图像资源
    protected function saveImage($imageRes,$newPath){
        $func = ‘image‘.$this->type;
        //通过变量函数进行保存
        $func($imageRes,$newPath);
    }
    //得到文件名函数
    protected function createNewName($imagePath,$prefix){
        if ($this->isRandName){
            $name = $prefix.uniqid().‘.‘.$this->type;
        }else {
            $name = $prefix.pathinfo($imagePath)[‘filename‘].‘.‘.$this->type;
        }
        return $name;
    }
    //根据位置计算水印图片的坐标
    protected function getPosition($postion,$imageInfo,$waterInfo){
        switch ($postion){
            case 1:
                $x = 0;
                $y = 0;
                break;
            case 2:
                $x = ($imageInfo[‘width‘]-$waterInfo["width"])/2;
                $y = 0;
                break;
            case 3:
                $x = $imageInfo["width"]- $waterInfo["width"];
                $y = 0;
                break;
            case 4:
                $x = 0;
                $y = ($imageInfo["height"]-$waterInfo["height"])/2;
                break;
            case 5:
                $x = ($imageInfo[‘width‘]-$waterInfo["width"])/2;
                $y = ($imageInfo["height"]-$waterInfo["height"])/2;
                break;
            case 6:
                $x = $imageInfo["width"]- $waterInfo["width"];
                $y = ($imageInfo["height"]-$waterInfo["height"])/2;
                break;
            case 7:
                $x = 0;
                $y = $imageInfo[‘height‘] - $waterInfo["height"];
                break;
            case 8:
                $x = ($imageInfo[‘width‘]-$waterInfo["width"])/2;
                $y = $imageInfo[‘height‘] - $waterInfo["height"];
                break;
            case 9:
                $x = $imageInfo["width"]- $waterInfo["width"];
                $y = $imageInfo[‘height‘] - $waterInfo["height"];
                break;
            case 0:
                $x = mt_rand(0, $imageInfo["width"]- $waterInfo["width"]);
                $y = mt_rand(0, $imageInfo[‘height‘] - $waterInfo["height"]);
                break;
        }
        return [‘x‘=>$x , ‘y‘=>$y];
    }
    protected function checkImage($imageInfo,$waterInfo){
        if (($waterInfo[‘width‘] > $imageInfo[‘width‘])||($waterInfo[‘height‘] > $imageInfo[‘height‘])){
            return false;
        }
        return true;
    }
    //静态方法。根据图片的路径得到图片的信息，宽度，高度、mime类型
    static function getImageInfo($imagePath){
        $info = getimagesize($imagePath);
        $data[‘width‘]=$info[0];
        $data[‘height‘]=$info[1];
        $data[‘mime‘] = $info[‘mime‘];
        return $data;
    }
    static function openAnyImage($imagePath){
        //得到图像的mime类型
        $mime = self::getImageInfo($imagePath)[‘mime‘];
        //根据不同的mime类型打开不同的图像
        switch ($mime){
            case ‘image/png‘:
                $image = imagecreatefrompng($imagePath);
                break;
            case ‘image/gif‘:
                $image = imagecreatefromgif($imagePath);
                break;
            case ‘image/jpeg‘:
                $image = imagecreatefromjpeg($imagePath);
                break;
            case ‘image/wbmp‘:
                $image = imagecreatefromwbmp($imagePath);
                break;
        }
        return $image;
    }

}