php gd等比例缩放压缩图片函数(好像也不能保证比例，不是正文形的会造成图片拉伸）

<?php
  /**
   * desription 判断是否gif动画
   * @param sting $image_file图片路径
   * @return boolean t 是 f 否
   */
  function check_gifcartoon($image_file){
    $fp = fopen($image_file,'rb');
    $image_head = fread($fp,1024);
    fclose($fp);
    return preg_match("/".chr(0x21).chr(0xff).chr(0x0b).'NETSCAPE2.0'."/",$image_head)?false:true;
  }
 
  /**
  * desription 压缩图片
  * @param sting $imgsrc 图片路径
  * @param string $imgdst 压缩后保存路径
  */
  function compressed_image($imgsrc,$imgdst){
    list($width,$height,$type)=getimagesize($imgsrc);
    $new_width = ($width>600?600:$width)*0.9;
    $new_height =($height>600?600:$height)*0.9;
    switch($type){
      case 1:
        $giftype=check_gifcartoon($imgsrc);
        if($giftype){
          header('Content-Type:image/gif');
          $image_wp=imagecreatetruecolor($new_width, $new_height);
          $image = imagecreatefromgif($imgsrc);
          imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
          //75代表的是质量、压缩图片容量大小
          imagejpeg($image_wp, $imgdst,75);
          imagedestroy($image_wp);
        }
        break;
      case 2:
        header('Content-Type:image/jpeg');
        $image_wp=imagecreatetruecolor($new_width, $new_height);
        $image = imagecreatefromjpeg($imgsrc);
        imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
        //75代表的是质量、压缩图片容量大小
        imagejpeg($image_wp, $imgdst,75);
        imagedestroy($image_wp);
        break;
      case 3:
        header('Content-Type:image/png');
        $image_wp=imagecreatetruecolor($new_width, $new_height);
        $image = imagecreatefrompng($imgsrc);
        imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
        //75代表的是质量、压缩图片容量大小
        imagejpeg($image_wp, $imgdst,75);
        imagedestroy($image_wp);
        break;
    }
  }

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