具体用法如下：
$a=thumbImage('1.jpg',200,100,'2.jpg');//将1.jpg生成宽为200，高为100的缩略图，并保存为2.jpg
print_r($a);打印结果：
Array(
[status] => 0
[file] => 1.jpg
[width] => 200
[height] => 200
[savePath] => 2.jpg
[info] => 缩略图片生成成功
)
$a=thumbImage('1.jpg',200,100);//将1.jpg生成宽为200，高为100的缩略图，并直接覆盖1.jpg，不生成新图片函数代码如下：
<?php
/*
*php生成图片缩略图的函数
*www.feishuai.vip
*/
function thumbImage($file,$thumbWidth,$thumbHeight,$savePath='',$isCut=true,$quality=100){
$result=array('status'=>0,'file'=>'','width'=>0,'height'=>0,'savePath'=>'','info'=>'');
if(!file_exists($file)){
return array('status'=>1,'file'=>'','width'=>0,'height'=>0,'savePath'=>'','info'=>'图片文件不存在');
}
//检测文件类型
$fp=fopen($file,'rb');
$str=fread($fp,2); //只读2字节
fclose($fp);
$str=@unpack("c2chars",$str);
$typeCode=intval($str['chars1'].$str['chars2']);
$fileType='';
switch($typeCode){
case 255216:
$fileType='jpg';
break;
case 7173:
$fileType='gif';
break;
case 6677:
$fileType='bmp';
break;
case 13780:
$fileType='png';
break;
default:
$fileType=$typeCode;
break;
}
if($str['chars1']=='-1'&&$str['chars2']=='-40'){
$fileType='jpg';
}
if($str['chars1']=='-119'&&$str['chars2']=='80'){
$fileType='png';
}
if(!in_array($fileType,array('jpg','gif','bmp','png'))){
return array('status'=>2,'file'=>'','width'=>0,'height'=>0,'savePath'=>'','info'=>'图片文件类型不正确:'.$fileType);
}
//图片缩放处理
if($fileType=='jpg'){
$im=imagecreatefromjpeg($file);
}
if($fileType=='gif'){
$im=imagecreatefromgif($file);
}
if($fileType=='png'){
$im=imagecreatefrompng($file);
}
if(empty($savePath))
$savePath=$file;
$width=imagesx($im);
$height=imagesy($im);
if($width<$thumbWidth&&$height<$thumbHeight){
return array('status'=>3,'file'=>'','width'=>0,'height'=>0,'savePath'=>'','info'=>'图片尺寸小于生成缩略图的尺寸');
}
$ratio=$width/$height;//实际图象的比例
$thumbRatio=$thumbWidth/$thumbHeight;//改变后的图象的比例
if($isCut){//裁切处理
if(function_exists('imagepng')&&(str_replace('.','',PHP_VERSION)>=512)){//针对php版本大于5.12参数变化后的处理情况
$quality=9;
}
if($ratio>=$thumbRatio){//高度优先
$newimg=imagecreatetruecolor($thumbWidth,$thumbHeight);
imagecopyresampled($newimg,$im,0,0,0,0,$thumbWidth,$thumbHeight,(($height)*$thumbRatio),$height);
imagejpeg($newimg,$savePath,$quality);
}
if($ratio<$thumbRatio){//宽度优先
$newimg=imagecreatetruecolor($thumbWidth,$thumbHeight);
imagecopyresampled($newimg,$im,0,0,0,0,$thumbWidth,$thumbHeight,$width,(($width)/$thumbRatio));
imagejpeg($newimg,$savePath,$quality);
}
}else{//不裁切处理
if($ratio>=$thumbRatio){
$newimg=imagecreatetruecolor($thumbWidth,($thumbWidth)/$ratio);
imagecopyresampled($newimg,$im,0,0,0,0,$thumbWidth,($thumbWidth)/$ratio,$width,$height);
imagejpeg($newimg,$savePath,$quality);
}
if($ratio<$thumbRatio){
$newimg=imagecreatetruecolor(($thumbHeight)*$ratio,$thumbHeight);
imagecopyresampled($newimg,$im,0,0,0,0,($thumbHeight)*$ratio,$thumbHeight,$width,$height);
imagejpeg($newimg,$savePath,$quality);
}
}
ImageDestroy($im);//www.feishuai.vip/php-function/1007.html
return array('status'=>0,'file'=>$file,'width'=>$thumbWidth,'height'=>$thumbHeight,'savePath'=>$savePath,'info'=>'缩略图片生成成功');
}