等比例缩放的，如果你指定的尺寸和缩放的比例不一致，会用纯色填补。
本人不才，第一次分享代码，欢迎拍砖！
<php
/**
* @abstract 生成图片的缩略图，可以指定任意尺寸，生成的图片为png格式
* @example
* $file = 'test.png';
* $th =new Thumbnail();
* $th->GenerateThumbnail($file, 400, 500);
*
*/
class Thumbnail{
/**
* @var string $from 源图片
*/
private $from;
/**
* @var string $name 缩略图的文件名
*/
private $name = '';
/**
* @var 原图宽
*/
private $rWidth;
/**
* @var 原图高
*/
private $rHeight;
/**
* @var 缩略图宽
*/
private $tWidth;
/**
* @var 缩略图高
*/
private $tHeight;
/**
* @var 实际缩放到的宽度
*/
private $width;
/**
* @var 实际缩放到的高度
*/
private $height;
public function __construct(){
try{
if(!function_exists('gd_info')){
throw new Exception('Must GD extension is enabled');
}
}
catch(Exception $e){
$msg = 'class ' . __CLASS__ . ' Error:' . $e->getMessage();
echo $msg;
exit;
}
}
/**
* @var $from 原图像
* @var $width 生成的缩略图的宽
* @var $height 生成缩略图的高
* @var $name 生成的缩略图的文件名，不带后缀
* @return string 生成的缩略图
*/
public function GenerateThumbnail($from, $width, $height, $name=''){
try{
if(!file_exists($from)){
throw new Exception('File does not exist');
}
if($width <= 0){
throw new Exception('The width is invalid');
}
if($height <= 0){
throw new Exception('The height is invalid');
}
$this->from = $from;
$this->tWidth = $width;
$this->tHeight = $height;
if(!empty($name)){
$this->name = $name;
}
else{
$this->name = date('Ymd') . mt_rand(0, 9999);
}
$this->createThumbnail();
}
catch(Exception $e){
$msg = 'class ' . __CLASS__ . ' Error:' . $e->getMessage();
echo $msg;
exit;
}
}
public function getThumbnail(){
return $this->name;
}
/**
* 生成缩略图文件
*/
private function createThumbnail(){
try{
//读取原始图像信息
$sourceInfo = getimagesize($this->from);
$this->rWidth = $sourceInfo[0];
$this->rHeight = $sourceInfo[1];
//创建缩略图图像资源句柄
$new_pic = imagecreatetruecolor($this->tWidth, $this->tHeight);
//原图绘制到缩略图的x、y坐标
$x = 0;
$y = 0;
//创建原始图像资源句柄
$source_pic = '';
switch ($sourceInfo[2]){
case 1: $source_pic = imagecreatefromgif($this->from); //gif
break;
case 2: $source_pic = imagecreatefromjpeg($this->from); //jpg
break;
case 3: $source_pic = imagecreatefrompng($this->from); //png
break;
default: throw new Exception('Does not support this type of image');
}
//计算缩放后图像实际大小
//原图宽高均比缩略图大
if($this->rWidth > $this->tWidth && $this->rHeight > $this->tHeight){
$midw = ($this->rWidth - $this->tWidth) / $this->rWidth; //宽缩小的比例
$midh = ($this->rHeight - $this->tHeight) / $this->rHeight; //高缩小的比例
//那个缩小的比例大以那个为准
if($midw > $midh){
$this->width = $this->tWidth;
$this->height = $this->rHeight - floor($this->rHeight * $midw);
$y = ($this->tHeight - $this->height) / 2;
}
else{
$this->width = $this->rWidth - floor($this->rWidth * $midh);
$this->height = $this->tHeight;
$x = ($this->tWidth - $this->width) / 2;
}
}
//原图宽高均比缩略图小
elseif($this->rWidth < $this->tWidth && $this->rHeight < $this->tHeight){
$midw = ($this->tWidth - $this->rWidth) / $this->rWidth; //宽放大的比例
$midh = ($this->tHeight - $this->rHeight) / $this->rHeight; //高放大的比例
//那个放大的比例小以那个为准
if($midw < $midh){
$this->width = $this->tWidth;
$this->height = $this->rHeight + floor($this->rHeight * $midw);
$y = ($this->tHeight - $this->height) / 2;
}
else{
$this->width = $this->rWidth + floor($this->rWidth * $midh);
$this->height = $this->tHeight;
$x = ($this->tWidth - $this->width) / 2;
}
}
//原图宽小于缩略图宽，原图高大于缩略图高
elseif($this->rWidth < $this->tWidth && $this->rHeight > $this->tHeight){
$mid = ($this->rHeight - $this->tHeight) / $this->rHeight; //高缩小的比例
$this->width = $this->rWidth - floor($this->rWidth * $mid);
$this->height = $this->rHeight - floor($this->rHeight * $mid);
$x = ($this->tWidth - $this->width) / 2;
$y = ($this->tHeight - $this->height) / 2;
}
//原图宽大于缩略图宽，原图高小于缩略图高
elseif($this->rWidth > $this->tWidth && $this->rHeight < $this->tHeight){
$mid = ($this->rWidth - $this->tWidth) / $this->rWidth; //宽缩小的比例
$this->width = $this->rWidth - floor($this->rWidth * $mid);
$this->height = $this->rHeight - floor($this->rHeight * $mid);
$x = ($this->tWidth - $this->width) / 2;
$y = ($this->tHeight - $this->height) / 2;
}
else{
throw new Exception('Resize error');
}
//给缩略图添加白色背景
$bg = imagecolorallocate($new_pic, 255, 255, 255);
imagefill($new_pic, 0, 0, $bg);
//缩小原始图片到新建图片
imagecopyresampled($new_pic, $source_pic, $x, $y, 0, 0, $this->width, $this->height, $this->rWidth, $this->rHeight);
//输出缩略图到文件
imagepng($new_pic, $this->name.'.png');
imagedestroy($new_pic);
imagedestroy($source_pic);
}
catch(Exception $e){
$msg = 'class ' . __CLASS__ . ' Error:' . $e->getMessage();
echo $msg;
exit;
}
}
}
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