纯前端导出带水印文件

首页 > 我的学习历程作者：月丶 2023年11月20日 15:25 星期一热度：293° 百度已收录

时间：2023-11-20 15:25 热度：293°

1、安装依赖
npm install exceljs file-saver html2canvas jspdf

2、导出方法
可导出图片，Excel文件

	
		import htmlTocanvas from 'html2canvas' 
	
		import ExcelJS from 'exceljs' 
	
		import jsPDF from 'jspdf' 
	
		import { saveAs } from 'file-saver'

		export const ExportUtil = {
	
		  /** 
	
		   * Generates a function comment for the given function body in a markdown code block with the correct language syntax. 
	
		   * 
	
		   * @param {Object} options - An object containing the function parameters. 
	
		   * @param {string} options.name - The name of the export. 
	
		   * @param {Array} options.data - The data to be exported. 
	
		   * @param {Array} options.columns - The columns to be included in the export. 
	
		   * @param {string} options.waterText - The watermark text to be added to the export. 
	
		   * @return {undefined} This function does not return a value. 
	
		   */ 
	
		  exportExcel ({ name = `${new Date().getTime()}`, data = [], columns = [], mergeColumns = [], waterText = true }) {
	
		    const workbook = new ExcelJS.Workbook()
	
		    const worksheet = workbook.addWorksheet('sheet1')
	
		    if (waterText) {
	
		      const defaultText = '测试水印' 
	
		      waterText = typeof waterText === 'string' ? waterText : defaultText 
	
		      const base64Img = this.setWatermark(waterText)
	
		      const img = workbook.addImage({
	
		        base64: base64Img,
	
		        extension: 'png' 
	
		      })
	
		      worksheet.addBackgroundImage(img)
	
		    }
	
		    if (columns && columns.length) {
	
		      // 设置列头 
	
		      const columnsData = columns.map((column) => {
	
		        return {
	
		          header: column.title,
	
		          key: column.dataIndex || column.field,
	
		          style: {
	
		            alignment: { horizontal: 'center', vertical: 'middle' }
	
		          },
	
		          width: 20 
	
		        }
	
		      })
	
		      worksheet.columns = columnsData 
	
		    }
	
		    if (mergeColumns && mergeColumns.length) {
	
		      // 设置合并的表头 
	
		      mergeColumns.forEach(item => {
	
		        const start = item.mergeCells.split(':')[0]
	
		        worksheet.mergeCells(item.mergeCells)
	
		        worksheet.getCell(start).value = item.value 
	
		        worksheet.getCell(start).alignment = { horizontal: 'center', vertical: 'middle' }
	
		        worksheet.getCell(start).font = { bold: true }
	
		      })
	
		    }
	
		    // 将 JSON 数据转换为工作表的行 
	
		    worksheet.addRows(data)
	
		    workbook.xlsx.writeBuffer().then((res) => {
	
		      saveAs(new Blob([res], { type: 'application/octet-stream' }), name.includes('.xlsx') ? name : `${name}.xlsx`)
	
		    })
	
  },
			
				  exportPDF ({ element, fileName, config = {}, waterText = true }) {
			
				    return new Promise((resolve, reject) => {
			
				      htmlTocanvas(element, {
			
				        useCORS: true,
			
				        backgroundColor: '#f7f7f8',
			
				        ...config 
			
				      }).then(canvas => {
			
				        let base64Img 
			
				        if (waterText) {
			
				          const userInfo = store.getters.userInfo 
			
				          const defaultText = '测试水印' 
			
				          waterText = typeof waterText === 'string' ? waterText : defaultText 
			
				          base64Img = this.setWatermark(waterText, canvas)
			
				        }
			
				        const imgData = base64Img || canvas.toDataURL('image/png')
			
				        const pdf = new jsPDF('p', 'pt', 'a4')
			
				        // 获取PDF页面的宽度和高度 
			
				        const pdfWidth = pdf.internal.pageSize.getWidth()
			
				        const pdfHeight = pdf.internal.pageSize.getHeight()
			
				        // 计算图像的缩放比例，使其铺满整个PDF页面 
			
				        const imgWidth = pdfWidth 
			
				        const imgHeight = (imgWidth * pdfHeight) / pdfWidth 
			
				        pdf.addImage(imgData, 'PNG', 0, 0, imgWidth, imgHeight)
			
				        pdf.save(fileName.includes('.pdf') ? fileName : `${fileName}.pdf`)
			
				        resolve()
			
				      }).catch(err => {
			
				        reject(err)
			
				      })
			
				    })
			
				  },
			
		  /** 
	
		   * Takes an HTML element and converts it to a canvas image, optionally adding a watermark text. 
	
		   * 
	
		   * @param {object} options - An object containing the following properties: 
	
		   *   @param {HTMLElement} options.element - The HTML element to convert to canvas. 
	
		   *   @param {string} options.fileName - The name of the file to be downloaded. 
	
		   *   @param {object} [options.config={}] - Additional configuration options for the HTML to canvas conversion. 
	
		   *   @param {boolean} [options.waterText=true] - Whether to add a watermark text to the image. 
	
		   * @return {Promise} A Promise that resolves when the image is downloaded. 
	
		   */ 
	
		  exportImg({ element, fileName, config = {}, waterText = true }) { 
	
		    return new Promise((resolve, reject) => {
	
		      htmlTocanvas(element, {
	
		        useCORS: true,
	
		        backgroundColor: '#f7f7f8',
	
		        ...config 
	
		      }).then(canvas => {
	
		        let base64Img 
	
		        if (waterText) {
	
		          const defaultText = '测试水印' 
	
		          waterText = typeof waterText === 'string' ? waterText : defaultText 
	
		          base64Img = this.setWatermark(waterText, canvas)
	
		        }
	
		        const link = document.createElement('a')
	
		        link.download = `${fileName || new Date().getTime()}.png` 
	
		        link.href = base64Img || canvas.toDataURL('image/png')
	
		        link.click()
	
		        resolve()
	
		      }).catch(err => {
	
		        reject(err)
	
		      })
	
		    })
	
		  },
	
		  /** 
	
		  * Sets a watermark on a canvas. 
	
		  * 如果是导出图片的话，必传canvas，导出excel的时候不需要传 
	
		  * 
	
		  * @param {string} str - The text of the watermark. 
	
		  * @param {HTMLCanvasElement} canvas - The canvas element to place the watermark on. If not provided, a new canvas will be created. 
	
		  * @return {string} - The data URL of the canvas with the watermark. 
	
		  */ 
	
		  setWatermark (str, canvas) {
	
		    // 创建一个画布 
	
		    let can = canvas || document.createElement('canvas')
	
		    if (!canvas) {
	
		      // 设置画布的长宽 
	
		      can.width = 500 
	
		      can.height = 400 
	
		    }
	
		    let ctx = can.getContext('2d')
	
		    ctx.font = '18px Vedana' 
	
		    // 设置填充绘画的颜色、渐变或者模式 
	
		    ctx.fillStyle = 'rgba(130, 142, 162, 0.5)' 
	
		    // 旋转角度 
	
		    ctx.rotate(-60 * Math.PI / 220)
	
		    // 设置文本内容的当前对齐方式 
	
		    ctx.textAlign = 'left' 
	
		    // 设置在绘制文本时使用的当前文本基线 
	
		    ctx.textBaseline = 'Middle' 
	
		    if (canvas) {
	
		      // 定义水印的间隔和偏移量 
	
		      const xOffset = -can.width / 2 // X轴偏移量 
	
		      const yOffset = -can.height / 2 // Y轴偏移量 
	
		      // 循环绘制水印文本 
	
		      for (let x = 0; x < can.width * 1.5; x += 400) {
	
		        for (let y = 0; y < can.height * 1.5; y += 300) {
	
		          ctx.fillText(str, x + xOffset, y + yOffset)
	
		        }
	
		      }
	
		    } else {
	
		      let initY = can.height 
	
		      ctx.fillText(str, 0, initY)
	
		    }
	
		    return can.toDataURL('image/png')
	
		  }
	
		}

3、使用
import ExportUtil from 'xxx'

ExportUtil.exportExcel({name: '导出文件',columns:[{field: test,title: 测试头}],data:[{test: 23}]})
ExportUtil.exportPDF({element: element, name:'导出PDF'})
ExportUtil.exportImg({element: element, name:'导出图片'})