exif_imagetype

(PHP 4 >= 4.3.0, PHP 5)

exif_imagetype — 判断一个图像的类型

说明

int exif_imagetype ( string $filename )

exif_imagetype() 读取一个图像的第一个字节并检查其签名。

本函数可用来避免调用其它 exif 函数用到了不支持的文件类型上或和 $_SERVER['HTTP_ACCEPT'] 结合使用来检查浏览器是否可以显示某个指定的图像。

参数

filename: 被检查的图像文件名。

返回值

如果发现了恰当的签名则返回一个对应的常量，否则返回 FALSE。返回值和 getimagesize() 返回的数组中的索引 2 的值是一样的，但本函数快得多。

更新日志

版本	说明
4.3.2	支持 JPC，JP2，JPX，JB2，XBM 以及 WBMP
4.3.0	支持 SWC

预定义常量

定义有以下常量，并代表了 exif_imagetype() 可能的返回值：

**图像类型常量**
值	常量
1	`IMAGETYPE_GIF`
2	`IMAGETYPE_JPEG`
3	`IMAGETYPE_PNG`
4	`IMAGETYPE_SWF`
5	`IMAGETYPE_PSD`
6	`IMAGETYPE_BMP`
7	`IMAGETYPE_TIFF_II`（Intel 字节顺序）
8	`IMAGETYPE_TIFF_MM`（Motorola 字节顺序）
9	`IMAGETYPE_JPC`
10	`IMAGETYPE_JP2`
11	`IMAGETYPE_JPX`
12	`IMAGETYPE_JB2`
13	`IMAGETYPE_SWC`
14	`IMAGETYPE_IFF`
15	`IMAGETYPE_WBMP`
16	`IMAGETYPE_XBM`

范例

Example #1 exif_imagetype() 例子


<?php

if (exif_imagetype("image.gif") != IMAGETYPE_GIF) {
    echo "The picture is not a gif";
}

?>

参见

getimagesize() - 取得图像大小

PHP手册 - N: 判断一个图像的类型

用户评论:

admin at leonard !spam challis dot com (03-Nov-2010 04:02)

Windows users: If you get the fatal error "Fatal error: Call to undefined function exif_imagetype()", and you have enabled php_exif.dll, make sure you enable php_mbstring.dll. You must put mbstring before exif in the php.ini, i.e.: extension=php_mbstring.dll extension=php_exif.dll You can check whether this has worked by calling phpinfo() and searching for exif.

tom dot ghyselinck at telenet dot be (13-Jan-2008 09:36)

If the function exif_imagetype() is not available, you can try the following workaround: if ( ! function_exists( 'exif_imagetype' ) ) { function exif_imagetype ( $filename ) { if ( ( list($width, $height, $type, $attr) = getimagesize( $filename ) ) !== false ) { return $type; } return false; } }

Tim (19-Nov-2007 04:40)

By trial and error, it seems that a file has to be 12 bytes or larger in order to avoid a "Read error!". Here's a work-around to avoid an error being thrown: // exif_imagetype throws "Read error!" if file is too small if (filesize($uploadfile) > 11) $mimetype = exif_imagetype($uploadfile); else $mimetype = false;

(10-Nov-2006 12:43)

Seems to give a 'Read error' warning if the size of the file is very small (2 bytes). I think this is because it needs a min 3 bytes to determine the file type

tom at tomvergote dot be (07-Feb-2004 10:11)

libexif can also be used to parse image info out of id3 tags: exif_read_data("mp3_with_2.4ID3TAGS, '', true, false);

tilmauder at yahoo dot com (06-Jul-2003 12:57)

After looking for hours, I found a very good source for exif related programs here: http://drewnoakes.com/code/exif/index.html It lists exif specifications (pdf), a few good links to exif related stuff. The best source I have found in my quest to understand exif better for use in php based exif tools.