public function excel(){
        $list = Db::table('news')->select();
        //导出的文件名称
        $file_name = date('Y-m-d_H:i:s') . '表格' . '.xls';
        $PHPExcel=new \PHPExcel();
        $PHPSheet = $PHPExcel->getActiveSheet();

        $PHPExcel->setActiveSheetIndex(0)->getStyle('A')->getAlignment()->setHorizontal(\PHPExcel_Style_Alignment::HORIZONTAL_CENTER);
        $PHPExcel->setActiveSheetIndex(0)->getStyle('B')->getAlignment()->setHorizontal(\PHPExcel_Style_Alignment::HORIZONTAL_CENTER);
        $PHPExcel->setActiveSheetIndex(0)->getStyle('C')->getAlignment()->setHorizontal(\PHPExcel_Style_Alignment::HORIZONTAL_CENTER);
        $PHPExcel->setActiveSheetIndex(0)->getStyle('D')->getAlignment()->setHorizontal(\PHPExcel_Style_Alignment::HORIZONTAL_CENTER);

        // 设置个表格标题
        $PHPSheet->setTitle("代理商");
        $PHPSheet->setCellValue("A1", "ID");
        $PHPSheet->setCellValue("B1", "标题");
        $PHPSheet->setCellValue("C1", "分类");
        $PHPSheet->setCellValue("D1", "图片地址");

        //设置表格宽度
        $PHPExcel->getActiveSheet()->getColumnDimension('A')->setWidth(20);
        $PHPExcel->getActiveSheet()->getColumnDimension('B')->setWidth(20);
        $PHPExcel->getActiveSheet()->getColumnDimension('C')->setWidth(20);
        $PHPExcel->getActiveSheet()->getColumnDimension('D')->setWidth(80);

        // 设置垂直居中
        $PHPExcel->setActiveSheetIndex(0)->getStyle('A')->getAlignment()->setHorizontal(\PHPExcel_Style_Alignment::HORIZONTAL_CENTER);
        $PHPExcel->setActiveSheetIndex(0)->getStyle('B')->getAlignment()->setHorizontal(\PHPExcel_Style_Alignment::HORIZONTAL_CENTER);
        $PHPExcel->setActiveSheetIndex(0)->getStyle('C')->getAlignment()->setHorizontal(\PHPExcel_Style_Alignment::HORIZONTAL_CENTER);
        $PHPExcel->setActiveSheetIndex(0)->getStyle('D')->getAlignment()->setHorizontal(\PHPExcel_Style_Alignment::HORIZONTAL_CENTER);

        $i = 2;
        foreach ($list as $k => $v) {
            $PHPSheet->setCellValue('A' . $i, '' . $v['id']);
            $PHPSheet->setCellValue('B' . $i, '' . $v['title']);
            $PHPSheet->setCellValue('C' . $i, '' . $v['category']);

            //获取到图片信息
            if ($v['thumbnail_pic_s']) {
                // 图片生成
                $objDrawing[$k] = new \PHPExcel_Worksheet_MemoryDrawing();
                // 截取图片的格式，用不同的方法
                $end[$k] = substr($v['thumbnail_pic_s'], -3);

                if ($end[$k] == 'jpg' || $end[$k] == 'peg') {
                    $img[$k] = @imagecreatefromjpeg($v['thumbnail_pic_s']);
                } else if ($end[$k] == 'png') {
                    $img[$k] = @imagecreatefrompng($v['thumbnail_pic_s']);
                } else if ($end[$k] == 'gif') {
                    $img[$k] = @imagecreatefromgif($v['thumbnail_pic_s']);
                }

                $objDrawing[$k]->setImageResource($img[$k]);
                $objDrawing[$k]->setRenderingFunction(\PHPExcel_Worksheet_MemoryDrawing::RENDERING_DEFAULT);//渲染方法

                $objDrawing[$k]->setMimeType(\PHPExcel_Worksheet_MemoryDrawing::MIMETYPE_DEFAULT);
            }

            $objDrawing[$k]->setHeight(20);//照片高度
            $objDrawing[$k]->setWidth(70); //照片宽度

            $objDrawing[$k]->setCoordinates('D' . $i);

            // 图片偏移距离
            $objDrawing[$k]->setOffsetX(12);
            $objDrawing[$k]->setOffsetY(12);
            $objDrawing[$k]->setWorksheet($PHPExcel->getActiveSheet());
//            $PHPSheet->setCellValue('D'.$i,''.$value['image_input']);
            $i++;
        }
        $PHPExcel->setActiveSheetIndex(0);
        $objWriter = \PHPExcel_IOFactory::createWriter($PHPExcel, "Excel2007");
        header('Content-Disposition: attachment;filename=' . $file_name);
        header('Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
        header('Cache-Control: max-age=0');
        $objWriter->save("php://output");  //文件通过浏览器下载
    }