php实现图片压缩处理

/**
 * 图片压缩处理
 * @param string $sFile 图片路径
 * @param int $iWidth 自定义图片宽度
 * @param int $iHeight 自定义图片高度
 */
function getThumb($sFile,$iWidth,$iHeight){
  //判断该图片是否存在
  if(!file_exists(public_path().$sFile)) return $sFile;
  //判断图片格式
  $attach_fileext = get_filetype($sFile);
  if (!in_array($attach_fileext, array('jpg','png','jpeg'))){
    return $sFile;
  }
  //压缩图片
  $sFileNameS = str_replace(".".$attach_fileext, "_".$iWidth.'_'.$iHeight.'.'.$attach_fileext, $sFile);
  //判断是否已压缩图片，若是则返回压缩图片路径
  if(file_exists(public_path().$sFileNameS)){
    return $sFileNameS;
  }
  //解决手机端上传图片被旋转问题
  if (in_array($attach_fileext, array('jpeg')) ){
    adjustPicOrientation(public_path().$sFile);
  }
  //生成压缩图片，并存储到原图同路径下
  resizeImage(public_path().$sFile, public_path().$sFileNameS, $iWidth, $iHeight);
  if(!file_exists(public_path().$sFileNameS)){
    return $sFile;
  }
  return $sFileNameS;
}

/**
 *获取文件后缀名
 */
function get_filetype($filename) {
  $extend = explode("." , $filename);
  return strtolower($extend[count($extend) - 1]);
}

/**
 * 解决手机上传图片被旋转问题
 * @param string $full_filename 文件路径
 */
function adjustPicOrientation($full_filename){
  $exif = exif_read_data($full_filename);
  if($exif && isset($exif['Orientation'])) {
    $orientation = $exif['Orientation'];
    if($orientation != 1){
      $img = imagecreatefromjpeg($full_filename);

      $mirror = false;
      $deg  = 0;

      switch ($orientation) {
        case 2:
          $mirror = true;
          break;
        case 3:
          $deg = 180;
          break;
        case 4:
          $deg = 180;
          $mirror = true;
          break;
        case 5:
          $deg = 270;
          $mirror = true;
          break;
        case 6:
          $deg = 270;
          break;
        case 7:
          $deg = 90;
          $mirror = true;
          break;
        case 8:
          $deg = 90;
          break;
      }
      if ($deg) $img = imagerotate($img, $deg, 0);
      if ($mirror) $img = _mirrorImage($img);
      //$full_filename = str_replace('.jpg', "-O$orientation.jpg", $full_filename);新文件名
      imagejpeg($img, $full_filename, 95);
    }
  }
  return $full_filename;
}

resizeImage(public_path().$sFile, public_path().$sFileNameS, $iWidth, $iHeight);

/**
 * 生成图片
 * @param string $im 源图片路径
 * @param string $dest 目标图片路径
 * @param int $maxwidth 生成图片宽
 * @param int $maxheight 生成图片高
 */
function resizeImage($im, $dest, $maxwidth, $maxheight) {
  $img = getimagesize($im);
  switch ($img[2]) {
    case 1:
      $im = @imagecreatefromgif($im);
      break;
    case 2:
      $im = @imagecreatefromjpeg($im);
      break;
    case 3:
      $im = @imagecreatefrompng($im);
      break;
  }

  $pic_width = imagesx($im);
  $pic_height = imagesy($im);
  $resizewidth_tag = false;
  $resizeheight_tag = false;
  if (($maxwidth && $pic_width > $maxwidth) || ($maxheight && $pic_height > $maxheight)) {
    if ($maxwidth && $pic_width > $maxwidth) {
      $widthratio = $maxwidth / $pic_width;
      $resizewidth_tag = true;
    }

    if ($maxheight && $pic_height > $maxheight) {
      $heightratio = $maxheight / $pic_height;
      $resizeheight_tag = true;
    }

    if ($resizewidth_tag && $resizeheight_tag) {
      if ($widthratio < $heightratio)
        $ratio = $widthratio;
      else
        $ratio = $heightratio;
    }


    if ($resizewidth_tag && !$resizeheight_tag)
      $ratio = $widthratio;
    if ($resizeheight_tag && !$resizewidth_tag)
      $ratio = $heightratio;
    $newwidth = $pic_width * $ratio;
    $newheight = $pic_height * $ratio;

    if (function_exists("imagecopyresampled")) {
      $newim = imagecreatetruecolor($newwidth, $newheight);
      imagecopyresampled($newim, $im, 0, 0, 0, 0, $newwidth, $newheight, $pic_width, $pic_height);
    } else {
      $newim = imagecreate($newwidth, $newheight);
      imagecopyresized($newim, $im, 0, 0, 0, 0, $newwidth, $newheight, $pic_width, $pic_height);
    }

    imagejpeg($newim, $dest);
    imagedestroy($newim);
  } else {
    imagejpeg($im, $dest);
  }
}