(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)
exif_imagetype — 判断一个图像的类型
$filename
) : intexif_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 $_SERVER['HTTP_ACCEPT'] 结合使用来检查浏览器是否可以显示某个指定的图像。
filename
如果发现了恰当的签名则返回一个对应的常量，否则返回
false。返回值和 getimagesize()
返回的数组中的索引 2 的值是一样的，但本函数快得多。
| 版本 | 说明 |
|---|---|
| 4.3.2 | 支持 JPC，JP2，JPX，JB2，XBM 以及 WBMP |
| 4.3.0 | 支持 SWC |
定义有以下常量，并代表了 exif_imagetype() 可能的返回值：
| 值 | 常量 |
|---|---|
| 1 | IMAGETYPE_GIF |
| 2 | IMAGETYPE_JPEG |
| 3 | IMAGETYPE_PNG |
| 4 | IMAGETYPE_SWF |
| 5 | IMAGETYPE_PSD |
| 6 | IMAGETYPE_BMP |
| 7 | IMAGETYPE_TIFF_II（Intel 字节顺序） |
| 8 |
IMAGETYPE_TIFF_MM（Motorola 字节顺序）
|
| 9 | IMAGETYPE_JPC |
| 10 | IMAGETYPE_JP2 |
| 11 | IMAGETYPE_JPX |
| 12 | IMAGETYPE_JB2 |
| 13 | IMAGETYPE_SWC |
| 14 | IMAGETYPE_IFF |
| 15 | IMAGETYPE_WBMP |
| 16 | IMAGETYPE_XBM |
Example #1 exif_imagetype() 例子
<?php
if (exif_imagetype("image.gif") != IMAGETYPE_GIF) {
echo "The picture is not a gif";
}
?>
to checking file is image, I used this:
function is_image($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;
}
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');
}
?>
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.
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 $type;
}
return false;
}
}
By trial and error, it seems that a file has to be 12 bytes or larger in order to avoid a "Read error!". Here's a work-around to avoid an error being thrown:
// exif_imagetype throws "Read error!" if file is too small
if (filesize($uploadfile) > 11)
$mimetype = exif_imagetype($uploadfile);
else
$mimetype = false;
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
libexif can also be used to parse image info out of id3 tags:
exif_read_data("mp3_with_2.4ID3TAGS, '', true, false);