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这篇文章主要介绍了支持png透明图片的php生成缩略图类分享,本文代码基于GD2图形库,实现支持png透明图片生成缩略图,需要的朋友可以参考下

注：此功能依赖GD2图形库

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

* date: 2014.11.13

*/

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;

}

}

?>

使用

使用时，直接调用类的构造函数即可，构造函数如下：

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

参数

$imgPath：原图片地址

$width：缩略图宽

$height：缩略图高

$isCut：是否裁剪，bool值

$savePath：缩略图地址（可以跟原图片地址相同）

示例

<?php

include "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");

?>

效果

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