code: public function rotate( $angle, $background = 'FFFFFF' )
      {
          $angle = intval( $angle );
          if ( !is_int( $angle ) || ( $angle < 0 ) || ( $angle > 360 ) )
          {
              throw new ezcBaseValueException( 'height', $height, 'angle < 0 or angle > 360' );
          }
  
          $angle = 360 - $angle;
          $background = "#{$background}";
  
          $this->addFilterOption(
              $this->getActiveReference(),
              '-background',
              $background
          );
  
          $this->addFilterOption(
              $this->getActiveReference(),
              '-rotate',
              $angle
          );
      }
docs: Adds a rotation filter
  
  @param int $angle Rotation angle, 0 <= angle <= 360
  @param string $color
  @return void