php中几个简单图片判断函数

int exif_imagetype ( string $filename )
1 imagetype_gif
2 imagetype_jpeg
3 imagetype_png
4 imagetype_swf
5 imagetype_ps教程d
6 imagetype_bmp
7 imagetype_tiff_ii (intel byte order)
8 imagetype_tiff_mm (motorola byte order) 
9 imagetype_jpc
10 imagetype_jp2
11 imagetype_jpx
12 imagetype_jb2
13 imagetype_swc
14 imagetype_iff
15 imagetype_wbmp
16 imagetype_xbm

*/
$img="image.gif";          //定义文件
if(exif_imagetype($img)!=imagetype_gif)     //判断文件类型
{
  echo "指定的图片不是gif图片";       //输出结果
}
else
{
  echo "指定的图片是gif图片";
}

/*
array exif_read_data ( string $filename [, string $sections = null [, bool $arrays = false [, bool $thumbnail = false ]]] )

*/

echo "test1.jpg:
n";         //输出文件名
$exif=exif_read_data('tests/test1.jpg','ifd0');     //读取文件1信息
             //根据结果判断
echo $exif===false ? "no header data found.
n":"image contains headers
n";
$exif=exif_read_data('tests/test2.jpg',0,true);     //读取文件2信息
echo "test2.jpg:
n";         //输出文件名
foreach($exif as $key=>$section)       //循环读取信息
{
  foreach($section as $name=>$val)
  {
    echo "$key.$name:$val
n";
  }
}
/*
test1.jpg:
no header data found.
test2.jpg:
file.filename: test2.jpg
file.filedatetime: 1017666176
file.filesize: 1240
file.filetype: 2
file.sectionsfound: any_tag, ifd0, thumbnail, comment
computed.html:
computed.height: 1
computed.width: 1
computed.iscolor: 1
computed.byteordermotorola: 1
computed.usercomment: exif test image.
computed.usercommentencoding: ascii
computed.copyright: photo (c) m.boerger, edited by m.boerger.
computed.copyright.photographer: photo (c) m.boerger
computed.copyright.editor: edited by m.boerger.
ifd0.copyright: photo (c) m.boerger
ifd0.usercomment: ascii
thumbnail.jpeginterchangeformat: 134
thumbnail.jpeginterchangeformatlength: 523
comment.0: comment #1.
comment.1: comment #2.
comment.2: comment #3end
thumbnail.jpeginterchangeformat: 134
thumbnail.thumbnail.height: 1
thumbnail.thumbnail.height: 1

//*/

$index="1";          //定义索引
$string=exif_tagname($index);       //获得图像索引的头信息
echo $string;          //输出结果

//

if(array_key_exists('file',$_request))
{
  $image=exif_thumbnail($_request['file'],$width,$height,$type);  //取得文件的缩略图
}
else              //如果数组不存在相应的键值
{
  $image=false;           //返回错误
}
if($image!==false)           //如果返回true
{
  header("content-type:".image_type_to_mime_type($type));   //发送头文件
  echo $image;           //输出缩略图
  exit;             //结束php教程代码
}
else              //如果返回错误
{
  echo "no thumbnail available";        //输出信息
}