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exif_imagetype

(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)

exif_imagetype — 判断一个图像的类型

说明

exif_imagetype(string $filename): int

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

示例 #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

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User Contributed Notes 7 notes

down

christophe dot tournayre at univ*bpclermont dot Fr ¶

8 years ago


Because I only want to check for jpeg or png from a memory string, this is my 2 functions that are quick and don't have any dependencies :

<?php
  function is_jpeg(&$pict)
  {
    return (bin2hex($pict[0]) == 'ff' && bin2hex($pict[1]) == 'd8');
  }

  function is_png(&$pict)
  {
    return (bin2hex($pict[0]) == '89' && $pict[1] == 'P' && $pict[2] == 'N' && $pict[3] == 'G');
  }
?>

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Tim ¶

14 years ago


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;

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admin at leonard !spam challis dot com ¶

11 years ago


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.

down

tom dot ghyselinck at telenet dot be ¶

14 years ago


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;
    }
}

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-13

vuatintac at yahoo dot com ¶

7 years ago


to checking file is image, I used this:

function is_image($path)
{
    $a = getimagesize($path);
    $image_type = $a[2];

    if(in_array($image_type , array(IMAGETYPE_GIF , IMAGETYPE_JPEG ,IMAGETYPE_PNG , IMAGETYPE_BMP)))
    {
        return true;
    }
    return false;
}

down

-17

Anonymous ¶

15 years ago


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

down

-19

tom at tomvergote dot be ¶

18 years ago


libexif can also be used to parse image info out of id3 tags:

exif_read_data("mp3_with_2.4ID3TAGS, '', true, false);

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