共有两种等比例缩略图方法可以借鉴
一、为类文件，实例化之后即可使用
二、为自定义方法，比较轻巧

类文件

复制代码 代码如下:

$resizeimage = new resizeimage("./shawn.jpg", "200", "100", "0","../pic/shawnsun.jpg");
//实例化下面的类,就能生成缩略图
//其中,源文件和缩略图地址可以相同,200,100分别代表宽和高，第四个参数为可选 0不截图，1为截图

复制代码 代码如下:

class resizeimage{
 
    //图片类型
    public $type;
    //实际宽度
    public $width;
    //实际高度
    public $height;
    //改变后的宽度
    public $resize_width;
    //改变后的高度
    public $resize_height;
    //是否裁图
    public $cut;
    //源图象
    public $srcimg;
    //目标图象地址
    public $dstimg;
    //临时创建的图象
    public $im;
    
    function resizeimage($img, $wid, $hei,$c,$dstpath){
    
          $this--->srcimg = $img;
          $this->resize_width = $wid;
          $this->resize_height = $hei;
          $this->cut = $c;
    
          //图片的类型
          $this->type = strtolower(substr(strrchr($this->srcimg,"."),1));
          //初始化图象
          $this->initi_img();
          //目标图象地址
          $this->dst_img($dstpath);
          //W & H
          $this->width  = imagesx($this->im);
          $this->height = imagesy($this->im);
          //生成图象
          $this->newimg();
          ImageDestroy ($this->im);
     }
    
    function newimg(){
    
        //改变后的图象的比例
        $resize_ratio = ($this->resize_width)/($this->resize_height);
        //实际图象的比例
        $ratio = ($this->width)/($this->height);
        
        if(($this->cut)=="1")
        //裁图
        {
            if($ratio>=$resize_ratio)
            //高度优先
            {
                $newimg = imagecreatetruecolor($this->resize_width,$this->resize_height);
                imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width,
                                   $this->resize_height, (($this->height)*$resize_ratio),
                                   $this->height
                );
                ImageJpeg ($newimg,$this->dstimg);
            }
            if($ratio<$resize_ratio)
            //宽度优先
            {
                $newimg = imagecreatetruecolor($this->resize_width,$this->resize_height);
                imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width,
                                   $this->resize_height, $this->width,
                                   (($this->width)/$resize_ratio)
                );
                ImageJpeg ($newimg,$this->dstimg);
            }
              }
        else
        //不裁图
        {
            if($ratio>=$resize_ratio)
            {
                $newimg = imagecreatetruecolor($this->resize_width,
                                               ($this->resize_width)/$ratio
                );
                imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width,
                                   ($this->resize_width)/$ratio, $this->width,
                                   $this->height
                );
                ImageJpeg ($newimg,$this->dstimg);
            }
            if($ratio<$resize_ratio)
            {
                $newimg = imagecreatetruecolor(($this->resize_height)*$ratio,
                                                $this->resize_height
                );
                imagecopyresampled($newimg, $this->im, 0, 0, 0, 0,
                                   ($this->resize_height)*$ratio,
                                   $this->resize_height, $this->width,
                                   $this->height
                );
                ImageJpeg ($newimg,$this->dstimg);
            }
        }
   }
    
    //初始化图象
    function initi_img(){
 
        if($this->type=="jpg")
        {
            $this->im = imagecreatefromjpeg($this->srcimg);
        }
        if($this->type=="gif")
        {
            $this->im = imagecreatefromgif($this->srcimg);
        }
        if($this->type=="png")
        {
            $this->im = imagecreatefrompng($this->srcimg);
        }
    }
    //图象目标地址
    function dst_img($dstpath){
    
        $full_length  = strlen($this->srcimg);
        $type_length  = strlen($this->type);
        $name_length  = $full_length-$type_length;
 
        $name = substr($this->srcimg,0,$name_length-1);
        $this->dstimg = $dstpath;
 
        //echo $this->dstimg;
    }
}
 
?>

自定义方法

复制代码 代码如下:

thumbs('shawn.jpg','shawnsun.jpg',100,100);
//参数属性类似于方法一

复制代码 代码如下:

 
function thumbs($FileName,$SaveTo,$SetW,$SetH){
    $IMGInfo= getimagesize($FileName);
    if(!$IMGInfo) return false;
        
    if($IMGInfo['mime']== "image/pjpeg" || $IMGInfo['mime']=="image/jpeg"){
        $ThisPhoto= imagecreatefromjpeg($FileName);
    }elseif($IMGInfo['mime']== "image/x-png" || $IMGInfo['mime']== "image/png"){
        $ThisPhoto= imagecreatefrompng($FileName);  
    }elseif($IMGInfo['mime']== "image/gif"){
        $ThisPhoto=imagecreatefromgif($FileName);
    }
    
    $width=$IMGInfo[0];
    $height=$IMGInfo[1];  
    $scalc = max($width/$SetW,$height/$SetH);
    $nw = intval($width/$scalc);
    $nh = intval($height/$scalc);
    echo "缩略大小：w$nw,h$nh
";
    
    if($SetW-$nw == 1){$nw = $SetW;}
    if($SetH-$nh == 1){$nh = $SetH;}
    echo "+修正1像素： w$nw,h$nh
";
    
    //补宽
    if($SetW-$nw > 0){
        $nh = $nh +(($nh/$nw) * ($SetW-$nw));
        echo "*需补宽".($SetW-$nw).",陪补高".(($nh/$nw) * ($SetW-$nw))." 
"; 
        $nw = $SetW;
    }
    //补高
    if($SetH-$nh > 0){
        $nw = $nw + (($nw/$nh) * ($SetH-$nh));
        echo "*需补高".($SetH-$nh).",陪补宽". (($nw/$nh) * ($SetH-$nh)) ."
";
        $nh = $SetH;
    }
    $nw = intval($nw);
    $nh = intval($nh);
    echo "+修正大小：w$nw,h$nh
";
    
    $px = ($SetW - $nw)/2;
    $py = ($SetH - $nh)/2;
    echo "窗口大小：w$SetW,h$SetH
";
    echo "+偏移修正：x$px,y$py
";
    
    $NewPhoto=imagecreatetruecolor($SetW,$SetH);
    imagecopyresized($NewPhoto,$ThisPhoto,$px,$py,0,0,$nw,$nh,$width,$height);
    ImageJpeg ($NewPhoto,$SaveTo);
    return true;
}
    
?>