How to compress images in php while maintaining clarity

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<?php
 
/**
 * 图片压缩类：通过缩放来压缩。如果要保持源图比例，把参数$percent保持为1即可。
 * 即使原比例压缩，也可大幅度缩小。数码相机4M图片。也可以缩为700KB左右。如果缩小比例，则体积会更小。
 * 结果：可保存、可直接显示。
 */
class imgCompression{
 
       private $src;
       private $image;
       private $imageinfo;
       private $percent = 0.5;
       /**
        * 图片压缩
        * @param $src 源图
        * @param float $percent  压缩比例
        */
       public function __construct($src, $percent=1)
       {
              $this->src = $src;
              $this->percent = $percent;
       }
 
 
       /** 高清压缩图片
        * @param string $saveName  提供图片名（可不带扩展名，用源图扩展名）用于保存。或不提供文件名直接显示
        */
       public function compressImg($saveName=&#39;&#39;)
       {
              $this->_openImage();
              if(!empty($saveName)) $this->_saveImage($saveName);  //保存
              else $this->_showImage();
       }
 
       /**
        * 内部：打开图片
        */
       private function _openImage()
       {
              list($width, $height, $type, $attr) = getimagesize($this->src);
              $this->imageinfo = array(
                     &#39;width&#39;=>$width,
                     &#39;height&#39;=>$height,
                     &#39;type&#39;=>image_type_to_extension($type,false),
                     &#39;attr&#39;=>$attr
              );
              $fun = "imagecreatefrom".$this->imageinfo[&#39;type&#39;];
              $this->image = $fun($this->src);
              $this->_thumpImage();
       }
       /**
        * 内部：操作图片
        */
       private function _thumpImage()
       {
              $new_width = $this->imageinfo[&#39;width&#39;] * $this->percent;
              $new_height = $this->imageinfo[&#39;height&#39;] * $this->percent;
              $image_thump = imagecreatetruecolor($new_width,$new_height);
              //将原图复制带图片载体上面，并且按照一定比例压缩,极大的保持了清晰度
              imagecopyresampled($image_thump,$this->image,0,0,0,0,$new_width,$new_height,
              $this->imageinfo[&#39;width&#39;],$this->imageinfo[&#39;height&#39;]);
              imagedestroy($this->image);
              $this->image = $image_thump;
       }
       /**
        * 输出图片:保存图片则用saveImage()
        */
       private function _showImage()
       {
              header(&#39;Content-Type: image/&#39;.$this->imageinfo[&#39;type&#39;]);
              $funcs = "image".$this->imageinfo[&#39;type&#39;];
              $funcs($this->image);
       }
       /**
        * 保存图片到硬盘：
        * @param  string $dstImgName  1、可指定字符串不带后缀的名称，使用源图扩展名 。
        * 2、直接指定目标图片名带扩展名。
        */
       private function _saveImage($dstImgName)
       {
              if(empty($dstImgName)) return false;
              $allowImgs = [&#39;.jpg&#39;, &#39;.jpeg&#39;, &#39;.png&#39;, &#39;.bmp&#39;, &#39;.wbmp&#39;,&#39;.gif&#39;];   
              //如果目标图片名有后缀就用目标图片扩展名 后缀，如果没有，则用源图的扩展名
              $dstExt =  strrchr($dstImgName ,".");
              $sourseExt = strrchr($this->src ,".");
              if(!empty($dstExt)) $dstExt =strtolower($dstExt);
              if(!empty($sourseExt)) $sourseExt =strtolower($sourseExt);
 
              //有指定目标名扩展名
              if(!empty($dstExt) && in_array($dstExt,$allowImgs)){
                     $dstName = $dstImgName;
              }elseif(!empty($sourseExt) && in_array($sourseExt,$allowImgs)){
                     $dstName = $dstImgName.$sourseExt;
              }else{
                     $dstName = $dstImgName.$this->imageinfo[&#39;type&#39;];
              }
              $funcs = "image".$this->imageinfo[&#39;type&#39;];
              $funcs($this->image,$dstName);
       }
 
       /**
        * 销毁图片
        */
       public function __destruct(){
              imagedestroy($this->image);
       }
 
}

// eg:
$source = &#39;img.jpg&#39;;//原图
$dst_img = &#39;img1.jpg&#39;; //可加存放路径
$percent = 1;  //压缩比例 原图压缩，不缩放

$image = new imgCompression($source,$percent);
$image->compressImg($dst_img);

?>

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