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;
  }
}