====== 縮圖 ======
http://my-web-design.blogspot.com/2007/10/phpgd2.html

<code>
<?php
//高精度的縮圖類別
/***************************************/
/*功 能：利用PHP的GD函式生成高質量縮圖*/
/*運行環境:PHP5.01/GD2*/
/*類別說明：
可以選擇是/否裁圖，是/否放大圖像。
如果裁圖則生成的圖的尺寸與您輸入的一樣。
原則：盡可能保持原圖完整

如果不裁圖，則按照原圖比例生成新圖
原則：根據比例以輸入的長或者寬為基準

如果不放大圖像，則當原圖尺寸不大於新圖尺寸時，維持原圖尺寸
*/

/*參數說明：
$imgout:輸出圖片的位址
$imgsrc:源圖片位址
$width:新圖的寬度
$height:新圖的高度
$cut:是否裁圖，1為是，0為否
$enlarge:是否放大圖像，1為是，0為否*/
/***************************************/
class resizeimage
{
//圖片類型
var $type;
//實際寬度
var $width;
//實際高度
var $height;
//改變後的寬度
var $resize_width;
//改變後的高度
var $resize_height;
//是否裁圖
var $cut;
//是否放大圖像
var $enlarge;
//來源圖檔
var $srcimg;
//目標圖檔位址
var $dstimg;
//臨時建立的圖檔
var $im;
//回傳狀態
var $status;

function resizeimage($imgout, $imgsrc, $width, $height,$cut,$enlarge)
{
//目標圖檔位址
$this->dstimg = $imgout;
//來源圖檔
$this->srcimg = $imgsrc;
//改變後的寬度
$this->resize_width = $width;
//改變後的高度
$this->resize_height = $height;
//是否裁圖
$this->cut = $cut;
//是否放大圖像
$this->enlarge = $enlarge;
//初始化圖檔
$this->initi_img();
//來源圖檔實際寬度
$this->width = imagesx($this->im);
//來源圖檔實際高度
$this->height = imagesy($this->im);
//生成新圖檔
$this->newimg();
//結束圖形
ImageDestroy ($this->im);
}
function newimg()
{
if(($this->cut)=="1")
//裁圖
{
if($this->enlarge=='0')//不放大圖像，只縮圖
{
//調整輸出的圖片大小，如不超過指定的大小則維持原大小
if($this->resize_width < $this->width)
$resize_width = $this->resize_width;
else
$resize_width = $this->width;

if($this->resize_height < $this->height)
$resize_height = $this->resize_height;
else
$resize_height = $this->height;
}
else//放大圖像
{
$resize_width = $this->resize_width;
$resize_height = $this->resize_height;
}

//改變後的圖檔的比例
$resize_ratio = ($this->resize_width)/($this->resize_height);
//實際圖檔的比例
$ratio = ($this->width)/($this->height);

if($ratio>=$resize_ratio)
//高度優先
{
$newimg = imagecreatetruecolor($resize_width,$resize_height);
//生成白色背景
$white = imagecolorallocate($newimg, 255, 255, 255);
imagefilledrectangle($newimg,0,0,$resize_width,$resize_height,$white);
imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $resize_width,$resize_height, (($this->height)*$resize_ratio), $this->height);
$this->status = ImageJpeg ($newimg,$this->dstimg);
}
if($ratio<$resize_ratio)
//寬度優先
{
$newimg = imagecreatetruecolor($resize_width,$resize_height);
//生成白色背景
$white = imagecolorallocate($newimg, 255, 255, 255);
imagefilledrectangle($newimg,0,0,$resize_width,$resize_height,$white);
imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $resize_width, $resize_height, $this->width, (($this->width)/$resize_ratio));
$this->status = ImageJpeg ($newimg,$this->dstimg);
}
}
else
//不裁圖
{
if($this->enlarge=='0')//不放大圖像，只縮圖
{
//調整輸出的圖片大小，如不超過指定的大小則維持原大小
if($this->resize_width < $this->width)
$resize_width = $this->resize_width;
else
$resize_width = $this->width;

if($this->resize_height < $this->height)
$resize_height = $this->resize_height;
else
$resize_height = $this->height;
}
else//放大圖像
{
$resize_width = $this->resize_width;
$resize_height = $this->resize_height;
}

//改變後的圖檔的比例
$resize_ratio = ($this->resize_width)/($this->resize_height);
//實際圖檔的比例
$ratio = ($this->width)/($this->height);

if($this->width>=$this->height) //圖片較寬
{
$newimg = imagecreatetruecolor($resize_width,($resize_height)/$ratio);
//生成白色背景
$white = imagecolorallocate($newimg, 255, 255, 255);
imagefilledrectangle($newimg,0,0,$resize_width,($resize_width)/$ratio,$white);
imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $resize_width, ($resize_width)/$ratio, $this->width, $this->height);
$this->status = ImageJpeg ($newimg,$this->dstimg);
}
if($this->width<$this->height) //圖片較高
{
$newimg = imagecreatetruecolor(($resize_height)*$ratio,$resize_height);
//生成白色背景
$white = imagecolorallocate($newimg, 255, 255, 255);
imagefilledrectangle($newimg,0,0,($resize_height)*$ratio,$resize_height,$white);
imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, ($resize_height)*$ratio, $resize_height, $this->width, $this->height);
$this->status = ImageJpeg ($newimg,$this->dstimg);
}
}
}
//初始化圖檔
function initi_img()
{
//取得圖片的類型
$getimgdata=@getimagesize($this->srcimg);
$this->type = $getimgdata['mime'];

//根據類型選擇讀取方式
if($this->type=='image/gif')
{
$this->im = imagecreatefromgif($this->srcimg);
}
else if($this->type=='image/png')
{
$this->im = imagecreatefrompng($this->srcimg);
}
else
{
$this->im = imagecreatefromjpeg($this->srcimg);
}
}
}
?> 
</code>

使用方式：
<code>
<?php
$resizeimage = new resizeimage('upload/imgout.jpg', 'upload/imgsrc.jpg', 320, 240,'0','0');
?>
</code>