php5.4以下模拟getimagesizefromstring

html5上传图片时可用php://input的数据流来运作.

例如:

if($in = fopen('php://input', "rb"))
    while($buff = fread($in, 4096))
        fwrite('e:\\1.jpg', $buff);

如果要得到图片信息,那只有getimagesize($filename),再打一次刚关闭的文件.
php里有一个getimagesizefromstring,但是要>=php5.4,但目前还没服务器还没用上这么高版本的php.

作为一个效率癖,这是不被允许的,有直接操纵数据流的方法吗?答案是有, php官方手册上有 "支持的协议和封装协议",其中的data://大家应该都很熟悉.

我们可以利用它完成在数据流中直接操纵图片(水印,缩略图之类),以下代码为了方便我就直接file_get_contents().

$file_path = 'http://www.baidu.com/img/shouye_b5486898c692066bd2cbaeda86d74448.gif';
$stream = file_get_contents($file_path);
print_r(getimagesize("data://text/plain;base64," . base64_encode($stream)));
$new_img = imagecreatefromgif("data://text/plain;base64," . base64_encode($stream));//或者$new_img = imagecreatefromstring($stream);

print_r($new_img);

imagejpeg($new_img, 'E:\WEB\uploads\test.jpg', 100);

成功转换格式了.

这个方法固然好,但一次base64看起来不是那么爽,还有更简单的吗?当然, stream_register_wrapper — 注册一个用 PHP 类实现的 URL 封装协议

我们看看代码:

class getImgStream{

    private $imgStream;
    private $position;

    function stream_open($path, $mode, $options, &$opened_path){
        $url = parse_url($path);
        $this->imgStream = $GLOBALS[$url["host"]];
        $this->position = 0;
        return true;
    }

    function stream_read($count){
        $ret = substr($this->imgStream, $this->position, $count);
        $this->position += strlen($ret);
        return $ret;
    }

    function stream_stat(){
        //maxmemory: 5 * 1024 * 1024;
        $fp = fopen("php://temp/maxmemory:5242880", 'r+');
        fwrite($fp, $this->imgStream);
        $fstat = fstat($fp);
        fclose($fp);
        return $fstat;
    }

    function stream_eof(){
        return $this->position >= strlen($this->imgStream);
    }

    function stream_tell(){
        return $this->position;
    }

    function stream_close(){
        unset($this->imgStream, $this->position);
    }

}

$file_path = 'http://www.baidu.com/img/shouye_b5486898c692066bd2cbaeda86d74448.gif';
$stream = file_get_contents($file_path);

stream_wrapper_register("image", "getImgStream");

print_r(getimagesize('image://stream'));
$new_img = imagecreatefromgif('image://stream');//或者$new_img = imagecreatefromstring($stream);
print_r($new_img);
imagejpeg($new_img, 'E:\WEB\uploads\test.jpg', 100);

 没有意外,因为这个函数支持PHP 4 >= 4.3.0, PHP 5,这样才像效率癖干的事,但代码看起来多了好多,而且小小的图片.也看不出多大效率.

经测试,同一张本地图片(300x800),方法一平均43ms,方法二平均39ms

更正,如果报getimagesize的stream does not support seeking,可能要在wrapper中加入seek的操作,加入以下代码

        function stream_seek($offset, $whence){
            $l = strlen($this->imgStream);
            $p = &$this->position;
            switch($whence){
                case SEEK_SET: $newPos = $offset;
                    break;
                case SEEK_CUR: $newPos = $p + $offset;
                    break;
                case SEEK_END: $newPos = $l + $offset;
                    break;
                default: return false;
            }
            $ret = ($newPos >= 0 && $newPos <= $l);
            if($ret)
                $p = $newPos;
            return $ret;
        }