PHP按最大宽高等比例缩放图片类

本来用phpthumb来缩略图片是十分方便的，但是最近在sae上写项目发现phpthumb在sae上保存文件时会出问题，想来实现一个简单的按最大宽高等比例缩放图片类也并不困难，于是便自己写了一个方便修改。

   需GD库支持，可支持jpg、jpeg、png、gif格式的图片，代码短小适合新手学习用

<?php

class slpic {

    //原图片文件，包含路径和文件名

    var $orpic;    

    //原图的临时图像

    var $tempic;

    //缩略图

    var $thpic;

    //原宽度

    var $width;    

    //原高度

    var $height;

    //图片类型

    var $type;

    //缩略后的宽度

    var $thwidth;

    //缩略后的高度

    var $thheight;

    

    function __construct($file){

        $this->orpic = $file;

        $infos = getimagesize($file);

        $this->width = $infos[0];

        $this->height = $infos[1];

        $this->type = $infos[2];

    }

    

    //根据用户所指定最大宽高来计算缩略图尺寸

    function cal_size($maxwidth, $maxheight){

        //缩略图最大宽度与最大高度比

        $thcrown = $maxwidth/$maxheight;    

        //原图宽高比

        $crown = $this->width/$this->height;    

        if($crown/$thcrown >= 1){

            $this->thwidth = $maxwidth;

            $this->thheight = $maxwidth/$crown;

        } else {

            $this->thheight = $maxheight;

            $this->thwidth = $maxheight*$crown;

        }

    }

    

    function init(){

        switch($this->type){

            case 1:        //GIF

                $this->tempic = imagecreatefromgif($this->orpic);

                break;

            case 2:        //JPG

                $this->tempic = imagecreatefromjpeg($this->orpic);

                break;

            case 3:        //PNG

                $this->tempic = imagecreatefrompng($this->orpic);

                break;

            default:

                echo '暂不支持该图片格式';

        }

    }



    function resize($maxwidth, $maxheight){

        //初始化图像

        $this->init();

        //计算出缩略图尺寸

        $this->cal_size($maxwidth, $maxheight);

        

        $this->thpic = imagecreatetruecolor($this->thwidth, $this->thheight);

        imagecopyresampled($this->thpic, $this->tempic, 0, 0, 0 ,0, $this->thwidth, $this->thheight, $this->width, $this->height);

    }

    

    function save($filename, $type){

        switch($type){

            case 'jpg':

            case 'jpeg':

                imagejpeg($this->thpic, $filename);

                break;

            case 'png':

                imagepng($$this->thpic, $filename);

                break;

            case 'gif':

                imagegif($$this->thpic, $filename);

                break;

            default:

                echo '暂不支持您所选择的格式';

        }

    }

}

?>