PHP生成图片缩略图类示例

class app_image_helper {
  protected $imgfilename;
  protected $imgwidth;
  protected $imgheight;
  protected $imgmime;
  protected $imgresource;
  static  $imgminelist
    = array(
      'jpeg' => 'image/jpeg',
      'gif' => 'image/gif',
      'png' => 'image/png',
      'wbmp' => 'image/wbmp',
    );
  /**
   * 根据文件名，初始化图片，
   * 计算出给定图片的宽、高、图片类型，并获取图片的资源保存到内存，便于下次使用
   * app_image_helper constructor.
   *
   * @param $filename
   */
  public function __construct($filename) {
    $this->imgfilename = $filename;
    list($this->imgwidth, $this->imgheight, $this->imgmime) = $this->getimageinfo($this->imgfilename);
    $this->imgresource = $this->getimageresource($this->imgfilename);
  }
  /**
   * 根据图片路径获取相关宽、高、mime类型信息
   *
   * @param $filename
   *
   * @return array|null
   */
  protected function getimageinfo($filename) {
    $result = null;
    if ( is_file($filename) ) {
      $tmpimageinfo = getimagesize($filename);
      if ( $tmpimageinfo ) {
        $result = array($tmpimageinfo[0], $tmpimageinfo[1], $tmpimageinfo['mime']);
      }
    }
    return $result;
  }
  /**
   * 将图片文件转为资源类类型
   *
   * @param $filename
   *
   * @return null|resource
   */
  protected function getimageresource($filename) {
    $image = null;
    if ( is_file($filename) ) {
      switch ($this->imgmime) {
        case self::$imgminelist['jpeg']:
          $image = imagecreatefromjpeg($filename);
          break;
        case self::$imgminelist['gif']:
          $image = imagecreatefromgif($filename);
          break;
        case self::$imgminelist['png']:
          $image = imagecreatefrompng($filename);
          break;
        case self::$imgminelist['wbmp']:
          $image = imagecreatefromwbmp($filename);
          break;
        default:
          break;
      }
    }
    return $image;
  }
  /**
   * 可根据固定宽，等比缩放图片；或根据百分比，等比缩放图片
   *
   * @param int $width
   * @param int $percent
   *
   * @return array|null
   */
  protected function getsizebyscale($width = 360, $percent = 1) {
    $result = null;
    if ( $this->imgwidth && $this->imgheight ) {
      if ( $width ) {
        $result = array($width, intval($width * $this->imgheight / $this->imgwidth));
      } elseif ( $percent ) {
        $result = array(intval($this->imgwidth * $percent), intval($this->imgheight * $percent));
      }
    }
    return $result;
  }
  /**
   * 外调
   *
   * @param int $percentorwidth int整数表示图片缩放为固定宽度，0.0~0.99999表示缩放百分比
   * @param null $filename
   * @param int $quality
   * @param bool $resample    重新采样图片，默认是
   *
   * @return bool
   */
  public function createimage($percentorwidth = 1, $filename = null, $quality = 75, $resample = true) {
    $result = false;
    $filename ? header('content-type: ' . $this->imgmime) : false;
    $size = $this->getsizebyscale(($percentorwidth <= 1) ? null : $percentorwidth, $percentorwidth);
    if ( $size ) {
      $thumb = imagecreatetruecolor($size[0], $size[1]);
      if ( $resample ) {
        imagecopyresampled($thumb, $this->imgresource, 0, 0, 0, 0, $size[0], $size[1], $this->imgwidth, $this->imgheight);
      } else {
        imagecopyresized($thumb, $this->imgresource, 0, 0, 0, 0, $size[0], $size[1], $this->imgwidth, $this->imgheight);
      }
      $result = imagejpeg($thumb, $filename, $quality);
    }
    return $result;
  }
}