PHP 实现图片上传并生成缩略图示例

一个比较简单的PHP生成缩略图程序，参数及代码都算得上精简。 经测试代码如下：

<?PHP
$FILENAME = image_name;

// 生成图片的宽度
$RESIZEWIDTH = 400;

// 生成图片的高度
$RESIZEHEIGHT = 400;

function ResizeImage($im,$maxwidth,$maxheight,$name){
    $width = imagesx($im);
    $height = imagesy($im);
    if(($maxwidth && $width > $maxwidth) || ($maxheight && $height > $maxheight)){
        if($maxwidth && $width > $maxwidth){
            $widthratio = $maxwidth / $width;
            $RESIZEWIDTH = true;
            }
        if($maxheight && $height > $maxheight){
            $heightratio = $maxheight / $height;
            $RESIZEHEIGHT = true;
            }
        if($RESIZEWIDTH && $RESIZEHEIGHT){
            if($widthratio < $heightratio){
                $ratio = $widthratio;
                }else{
                $ratio = $heightratio;
                }
            }elseif($RESIZEWIDTH){
            $ratio = $widthratio;
            }elseif($RESIZEHEIGHT){
            $ratio = $heightratio;
            }
        $newwidth = $width * $ratio;
        $newheight = $height * $ratio;
        if(function_exists(imagecopyresampled)){
          
            $newim = imagecreatetruecolor($newwidth,$newheight);
            imagecopyresampled($newim,$im,$newwidth,$newheight,$width,$height);
            }else{
            $newim = imagecreate($newwidth,$newheight);
            imagecopyresized($newim,$height);
            }
        ImageJpeg ($newim,$name . .jpg);
        ImageDestroy ($newim);
        }else{
        ImageJpeg ($im,$name . .jpg);
        }
    }

if($_FILES['image']['size']){
    if($_FILES['image']['type'] == image/pjpeg){
        $im = imagecreatefromjpeg($_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($im){
        if(file_exists($FILENAME.jpg)){
            unlink($FILENAME.jpg);
            }
        ResizeImage($im,$RESIZEWIDTH,$RESIZEHEIGHT,$FILENAME);
        ImageDestroy ($im);
        }
    }

/*** 来自：编程之家 jb51.cc（jb51.cc） ***/ 
?>

HTML 经测试代码如下：

<img src=<? echo($FILENAME..jpg?reload=.rand(0,999999)); ?>><br><br>

<form enctype=multipart/form-data method=post>
<br>
<input type=file name=image size=50 value=浏览><p>
<input type=submit value=上传图片>
</form>

</body>
</html>

<!--   来自 编程之家 jb51.cc （jb51.cc）-->