PHP生成缩略图

刚刚写完的，可自定义大小生成缩略图。

<?php 

	$pic_name=date("dMYHis"); 

	// 生成图片的宽度 
	$pic_width=$_POST['width'];

	// 生成图片的高度 
	$pic_height=$_POST['length']; 

	function ResizeImage($im,$maxwidth,$maxheight,$name){ 
		//取得当前图片大小
		$width = imagesx($im); 
		$height = imagesy($im); 
		//生成缩略图的大小
		if(($width > $maxwidth) || ($height > $maxheight)){ 
			$widthratio = $maxwidth/$width; 	
			$heightratio = $maxheight/$height;  
			if($widthratio < $heightratio){ 
				$ratio = $widthratio; 
			}else{ 
				$ratio = $heightratio; 
			} 
			$newwidth = $width * $ratio; 
			$newheight = $height * $ratio; 
		
			if(function_exists("imagecopyresampled")){ 
				$newim = imagecreatetruecolor($newwidth, $newheight); 
				imagecopyresampled($newim, $im, 0, 0, 0, 0, $newwidth, $newheight, $width, $height); 
			}else{ 
				$newim = imagecreate($newwidth, $newheight); 
				imagecopyresized($newim, $im, 0, 0, 0, 0, $newwidth, $newheight, $width, $height); 
			} 
			ImageJpeg ($newim,$name . ".jpg"); 
			ImageDestroy ($newim); 
		}else{ 
			ImageJpeg ($im,$name . ".jpg"); 
		} 
	} 

	if($_FILES['image']['size']){ 
		//echo $_FILES['image']['type'];
		if($_FILES['image']['type'] == "image/pjpeg"||$_FILES['image']['type'] == "image/jpg"||$_FILES['image']['type'] == "image/jpeg"){ 
			$im = imagecreatefromjpeg($_FILES['image']['tmp_name']); 
		}elseif($_FILES['image']['type'] == "image/x-png"){ 
			$im = imagecreatefrompng($_FILES['image']['tmp_name']); 
		}elseif($_FILES['image']['type'] == "image/gif"){ 
			$im = imagecreatefromgif($_FILES['image']['tmp_name']); 
		}
		if($im){ 
			if(file_exists($pic_name.'.jpg')){ 
				unlink($pic_name.'.jpg'); 
			} 
			ResizeImage($im,$pic_width,$pic_height,$pic_name); 
			ImageDestroy ($im); 
		} 
	} 
?> 

<img src="<? echo $pic_name.'.jpg'; ?>"><br><br> 
<form enctype="multipart/form-data" method="post" action="small_picture.php"> 
<br> 
<input type="file" name="image" size="50" value="浏览"><p> 
生成缩略图宽度：<input type="text" name="width" size="5"><p>
生成缩略图长度：<input type="text" name="length" size="5"><p>
<input type="submit" value="上传图片"> 
</form>