图片压缩（1次）

• 只针对限定1M

  $data = file_get_contents("输入路径");
  $maxSize = 1 * 1024 * 1024;
  //图片进行压缩
  $data = compressImage($data, $maxSize);
  file_put_contents("输出路径", $data);
  function compressImage($data, $maxSize) {
      $size = strlen($data);
      $img = imagecreatefromstring($data);
      $width = imagesx($img);
      $height = imagesy($img);
      $percent = 1;
      $tmpWidth = $width;
      $tmpHeight = $height;
      while ($size > $maxSize) {
          $tmpPercent = round(log($maxSize, $size), 1);
          $tmpPercent = $tmpPercent == 1 ? $tmpPercent - 0.1 : $tmpPercent;
          $tmpWidth = $tmpWidth * $tmpPercent;
          $tmpHeight = $tmpHeight * $tmpPercent;
          $size = $tmpWidth * $tmpHeight / 0.95;//输出的是png,只适用于1M
          //$size = $tmpWidth * $tmpHeight / 8;//输出的是jpg
          $percent = $percent * $tmpPercent;
      }
      $newWidth = $width * $percent;
      $newHeight = $height * $percent;
      $newImg = imagecreatetruecolor($newWidth, $newHeight);
      imagecopyresampled($newImg, $img, 0, 0, 0, 0, floor($newWidth), floor($newHeight), $width, $height);
      ob_start(); //Turn on output buffering
      imagepng($newImg); //Generate your image
      $data = $output = ob_get_contents(); // get the image as a string in a variable
      ob_end_clean(); //Turn off output buffering and clean it
      imagedestroy($newImg);
      print_r("
  percent={$percent},newWidth={$newWidth},newHeight={$newHeight},size={$size}");
      return $data;
  }