PHP高质量不失真等比例图片缩放类

php图片缩放类,php不失真图片缩放类,php高质量缩略图,php缩略图函数,php无损缩放,php图片缩放后模糊解决,图片缩略图质量低解决方法。在PHP网站开发过程中，如果你建立的网站涉及大量的图片处理，必然涉及到图片上传、缩放，而如何保持图片不失真，是很多初级PHP网站开发者比较头疼的一件事，今天未来往事<https://www.fity.cn>就和大家分享一下如何进行等比例不失真图片缩放。

**首先我们来了解几个php函数：**
**imagepng()：**http://cn2.php.net/manual/en/function.imagepng.php
注：函数的第三个参数的数值区间控制图片的质量，与imagejpeg()函数不同，imagepng()函数的区间值是0-9 (0表示质量最高,9表示质量最低)。PHP 5.1.2+支持。
**imagegif()：**http://cn2.php.net/manual/en/function.imagegif.php
**imagejpeg()：**http://cn2.php.net/manual/en/function.imagejpeg.php
**注：**函数的第三个参数控制图片的质量,区间0-100 (0表示质量最低,100表示质量最高. 默认75)

```php
<?php  
  
class resizeimage    
{    
   //图片类型    
   protected $type;    
   //实际宽度    
   protected $width;    
   //实际高度    
   protected $height;    
   //改变后的宽度    
   protected $resize_width;    
   //改变后的高度    
   protected $resize_height;    
   //是否裁图, 默认为1进行裁切 以最大尺寸优先进行缩放后再进行裁切。当为0时等比例缩放
   protected $cut;    
   //源图象    
   protected $srcimg;    
   //目标图象地址  
   protected $dstimg;    
   //临时创建的图象   
   protected $im;    
    
   public function process($img, $wid, $hei,$cut=1,$dst_img)  //源图像 | 宽 | 高 | 是否裁切 | 目标地址  
   {    
       $this->srcimg = $img;    
       $this->resize_width = $wid;    
       $this->resize_height = $hei;    
       $this->cut = $cut;    
       //图片的类型    
       $this->type = substr(strrchr($this->srcimg,"."),1);    
       //初始化图象    
       $this->init_img();  
       //目标图象地址    
       $this -> dst_img($dst_img);  
       //--    
       $this->width = imagesx($this->im);    
       $this->height = imagesy($this->im);    
       //生成图象    
       $this->newimg();    
       ImageDestroy ($this->im);    
   }   
   //欢迎来访未来往事<https://www.fity.cn>  
   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(($this->cut)=="1")    
       //裁图  
       {    
           if($ratio>=$resize_ratio)    
           //高度优先    
           {    
               $newimg = imagecreatetruecolor($this->resize_width,$this->resize_height);    
               imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width,$this->resize_height, (($this->height)*$resize_ratio), $this->height);    
               $this->quality_deal($newimg);  
           }    
           if($ratio<$resize_ratio)    
           //宽度优先    
           {    
               $newimg = imagecreatetruecolor($this->resize_width,$this->resize_height);    
               imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, $this->resize_height, $this->width, (($this->width)/$resize_ratio));    
               $this->quality_deal($newimg);  
           }    
       }    
       else    
       //不裁图    
       {    
           if($ratio>=$resize_ratio)    
           {    
               $newimg = imagecreatetruecolor($this->resize_width,($this->resize_width)/$ratio);    
               imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, ($this->resize_width)/$ratio, $this->width, $this->height);    
               $this->quality_deal($newimg);  
           }    
           if($ratio<$resize_ratio)    
           {    
               $newimg = imagecreatetruecolor(($this->resize_height)*$ratio,$this->resize_height);    
               imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, ($this->resize_height)*$ratio, $this->resize_height, $this->width, $this->height);    
               $this->quality_deal($newimg);  
           }    
       }  
       
   }   
   //初始化图象      欢迎来访未来往事<https://www.fity.cn>  
   private function init_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($dst_img)    
   {    
       $full_length  = strlen($this->srcimg);    
       $type_length  = strlen($this->type);    
       $name_length  = $full_length-$type_length;    
       //$name         = substr($this->srcimg,0,$name_length-1);    
       //$this->dstimg = $name."_new.".$this->type;    
       $this->dstimg = $dst_img;  
  
   }  
     
   //缩略图质量处理 By:未来往事<https://www.fity.cn  rinald@www.fity.cn>  
   private function quality_deal($newimg){  
       
     $ext_type = strtolower($this->type);  
  
     if( $ext_type === 'jpg' || $ext_type === 'jpeg' ){  
       ImageJpeg ($newimg,$this->dstimg,100); //图片质量100-0  
     }elseif($ext_type === 'png'){  
       imagepng ($newimg,$this->dstimg,0); //图片质量0-9  
     }elseif($ext_type === 'gif'){  
       imagegif ($newimg,$this->dstimg);  
     }else{  
       ImageJpeg ($newimg,$this->dstimg);  
     }  
       
   }  
     
}  
  
//使用方法  
$resizeimage = new resizeimage();
$resizeimage->process('./p1.jpg', '224', '126', '1', './p1_224x126.jpg');
```

本文最后更新于 2019-06-27 13:57:04 并被添加「php php基础 php函数 php类」标签，已有 5557 位童鞋阅读过。

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