图片压缩之三（php实现）

<?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>