最近要用php生成缩略图，在网上找了一下，发现了这篇文章：PHP生成图片缩略图

试用了一下后，发现有这样几个问题：

1、png图片生成的缩略图是jpg格式的

2、png图片生成的缩略图没有了透明（半透明）效果（填充了黑色背景）

3、代码语法比较老

因此，在这个版本的基础上简单修改优化了一下。

PHP生成缩略图类

<?php/** desc: Resize Image(png, jpg, gif)* author: 十年后的卢哥哥(http://www.cnblogs.com/lurenjiashuo/)* date: 2014.11.13* base from: http://www.oschina.net/code/snippet_5189_2491*/class ResizeImage {//图片类型private $type;//实际宽度private $width;//实际高度private $height;//改变后的宽度private $resize_width;//改变后的高度private $resize_height;//是否裁图private $cut;//源图象private $srcimg;//目标图象地址private $dstimg;//临时创建的图象private $im;function __construct($imgPath, $width, $height, $isCut, $savePath) {$this->srcimg = $imgPath;$this->resize_width = $width;$this->resize_height = $height;$this->cut = $isCut;//图片的类型$this->type = strtolower(substr(strrchr($this->srcimg,"."),1));//初始化图象$this->initi_img();//目标图象地址$this -> dst_img($savePath);//--$this->width = imagesx($this->im);$this->height = imagesy($this->im);//生成图象$this->newimg();ImageDestroy ($this->im);}private function newimg() {//改变后的图象的比例$resize_ratio = ($this->resize_width)/($this->resize_height);//实际图象的比例$ratio = ($this->width)/($this->height);if($this->cut) {//裁图$newimg = imagecreatetruecolor($this->resize_width,$this->resize_height);if($this->type=="png") {imagefill($newimg, 0, 0, imagecolorallocatealpha($newimg, 0, 0, 0, 127));}if($ratio>=$resize_ratio) {//高度优先imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width,$this->resize_height, (($this->height)*$resize_ratio), $this->height);} else {//宽度优先imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, $this->resize_height, $this->width, (($this->width)/$resize_ratio));}} else {//不裁图if($ratio>=$resize_ratio) {$newimg = imagecreatetruecolor($this->resize_width,($this->resize_width)/$ratio);if($this->type=="png") {imagefill($newimg, 0, 0, imagecolorallocatealpha($newimg, 0, 0, 0, 127));}imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, ($this->resize_width)/$ratio, $this->width, $this->height);} else {$newimg = imagecreatetruecolor(($this->resize_height)*$ratio,$this->resize_height);if($this->type=="png") {imagefill($newimg, 0, 0, imagecolorallocatealpha($newimg, 0, 0, 0, 127));}imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, ($this->resize_height)*$ratio, $this->resize_height, $this->width, $this->height);}}if($this->type=="png") {imagesavealpha($newimg, true);imagepng ($newimg,$this->dstimg);} else {imagejpeg ($newimg,$this->dstimg);}}//初始化图象private function initi_img() {if($this->type=="jpg") {$this->im = imagecreatefromjpeg($this->srcimg);}if($this->type=="gif") {$this->im = imagecreatefromgif($this->srcimg);}if($this->type=="png") {$this->im = imagecreatefrompng($this->srcimg);}}//图象目标地址private function dst_img($dstpath) {$full_length  = strlen($this->srcimg);$type_length  = strlen($this->type);$name_length  = $full_length-$type_length;$name         = substr($this->srcimg,0,$name_length-1);$this->dstimg = $dstpath;}}
?>

$resizeimage = new resizeimage($imgPath, $width, $height, $isCut, $savePath);　

<?phpinclude "ResizeImage.php";//jpg$jpgResize = new ResizeImage("img/test_1920_1200.jpg", 320, 240, false, "img/test_320_240.jpg");//png$pngResize = new ResizeImage("img/test_1024_746.png", 320, 240, false, "img/test_320_240.png");?>