php中几个简单图片判断函数

*/
$img="image.gif"; //定义文件
if(exif_imagetype($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: width="1" height="1"
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
}

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