PHP 实现图片上传并生成缩略图示例

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<?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, 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($_FILES['image']['size']){
    if($_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：php教程（www.idcnote.com） ***/ 
?>

<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 php教程 （www.idcnote.com）-->

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