code: public function scalePercent( $width, $height )
      {
          if ( !is_int( $height ) || $height < 1 )
          {
              throw new ezcBaseValueException( 'height', $height, 'int > 0' );
          }
  
          if ( !is_int( $width ) || $width < 1 )
          {
              throw new ezcBaseValueException( 'width', $width, 'int > 0' );
          }
          $this->addFilterOption( $this->getActiveReference(),
              '-resize',
              "{$width}%x{$height}%"
          );
      }
docs: /*
  Reimplementation of the very same function of the parent class
  but without the restriction on the width.
  See related issue: http://issues.ez.no/IssueView.php?Id=15976&
  
  @see lib/ezc/ImageConversion/src/handlers/ezcImageImagemagickHandler#scalePercent($width, $height)