关于javascript:Javascript-html2canvas-jsPDF-导出PDF解决一半文字在上一页一半文字在下一页的问题

        var pdfContent = document.getElementById("pdfDiv");        var width = pdfContent.offsetWidth; //获取dom 宽度        var height = pdfContent.offsetHeight; //获取dom 高度        var canvas = document.createElement("canvas"); //创立一个canvas节点        var scale = 3; //定义任意放大倍数 反对小数，越大越清晰        var offsetTop = pdfContent.offsetTop;        var rect = pdfContent.getBoundingClientRect();//获取元素绝对于视察的偏移量        canvas.width = width * scale; //定义canvas 宽度 * 缩放        canvas.height = (height + offsetTop) * scale; //定义canvas（高度 +偏移量 ）*缩放        var content = canvas.getContext("2d");        content.scale(scale, scale); //获取context,设置scale        content.translate(-rect.left, -rect.top);//设置context地位，值为绝对于视窗的偏移量负值，让图片复位        // content.translate(-rect.left, -rect.top + 135);//设置context地位，值为绝对于视窗的偏移量负值，让图片复位        var opts = {            background: "#fff",            scale: scale, // 增加的scale 参数            canvas: canvas, //自定义 canvas            // logging: true, //日志开关，便于查看html2canvas的外部执行流程            width: width, //dom 原始宽度            height: height,            useCORS: true, // 【重要】开启跨域配置            allowTaint: true,            taintTest: false,            // scrollY: 0,            // scrollX: 0        };        html2canvas(pdfContent,opts ).then(function (canvas) {            downloadCanvasWithMargin(canvas);        })        //-----------------------        function downloadCanvasWithMargin(canvas){        //敞开锯齿        var context = canvas.getContext('2d');        context.mozImageSmoothingEnabled = false;        context.webkitImageSmoothingEnabled = false;        context.msImageSmoothingEnabled = false;        context.imageSmoothingEnabled = false;        let contentWidth = canvas.width;        let contentHeight = canvas.height;        //一页pdf显示html页面生成的canvas高度;        let pageHeight = contentWidth / 595.28 * 841.89;        //未生成pdf的html页面高度        let leftHeight = contentHeight;        let cutStartHeight = 0;        let canvasArr = [];        if(leftHeight > pageHeight) {            while (leftHeight > 0) {                //复制出(0, cutStartHeight)开始，contentWidth宽和pageHeight高的图片                let cutImage = context.getImageData(0, cutStartHeight, contentWidth, pageHeight);                //以通明背景开始，抛弃                if(cutImage.data[0] === 0 ){                    leftHeight -= pageHeight;                    cutStartHeight += pageHeight;                    continue;                }                //从图像底部开始校验色彩，直到验证到已红色结尾才开始切图像                let moveUpPx = 0; //上移px数                let totalLength = cutImage.data.length;                let lineLength = 4 * contentWidth * 1; //一行的data容量                let leftLength = totalLength - lineLength;                let rightLength = totalLength;                let circle = 0; //循环次数                let pointRatio = 0.98; //一行非给定色彩的占比系数                let pointRatioNum = contentWidth * pointRatio;                while( circle === moveUpPx ){                    circle ++;                    let ignorePoint = 0;                    for(let i = leftLength; i< rightLength ; i+=4){                        if(cutImage.data[i] === 255 || cutImage.data[i] === 251){                            if(cutImage.data[i] === cutImage.data[i+1] && cutImage.data[i] === cutImage.data[i+2]){                                ignorePoint++;                            }                        }                    }                    if(ignorePoint < pointRatioNum){                        leftLength -= lineLength;                        rightLength -= lineLength;                        moveUpPx ++;                    }                }                if(moveUpPx > 0){                    cutImage = context.getImageData(0, cutStartHeight, contentWidth, pageHeight - moveUpPx);                }                leftHeight -= pageHeight + moveUpPx;                cutStartHeight += pageHeight - moveUpPx;                //创立新图片                let nCanvas = document.createElement("canvas"); //创立一个canvas节点                nCanvas.width = canvas.width;                nCanvas.height = pageHeight - moveUpPx;                let nContext = nCanvas.getContext("2d");                nContext.mozImageSmoothingEnabled = false;                nContext.webkitImageSmoothingEnabled = false;                nContext.msImageSmoothingEnabled = false;                nContext.imageSmoothingEnabled = false;                nContext.putImageData(cutImage, 0, 0)                canvasArr.push(nCanvas);            }        }else{            canvasArr.push(canvas);        }        //解决尾页图片通明背景        let lastCanvas = canvasArr[canvasArr.length - 1];        let ctx = lastCanvas.getContext("2d");        // 将canvas的通明背景设置成红色--解决translate后便彩色背景的问题        let imageData = ctx.getImageData(0, 0, lastCanvas.width, lastCanvas.height);        for(var i = 0; i < imageData.data.length; i += 4) {            // 当该像素是通明的，则设置成红色            if(imageData.data[i + 3] === 0) {                imageData.data[i] = 255;                imageData.data[i + 1] = 255;                imageData.data[i + 2] = 255;                imageData.data[i + 3] = 255;            }        }        ctx.putImageData(imageData, 0, 0);        var pdf = new jsPDF('', 'pt', 'a4');        let leftMargin = 20;        let topMargin = 20;        let a4Width = 595.28;        let a4Height = 841.89;        let imgWidth = a4Width - leftMargin * 2;        let imgHeight = a4Height - 2 * topMargin;        for(let i =0; i < canvasArr.length; i++){            let curCanvas = canvasArr[i];            let pageData = curCanvas.toDataURL('image/jpeg', 1.0);            //小于切分的高度，要换算比例高            if(curCanvas.height < pageHeight){                let ratioHeight = imgWidth / curCanvas.width * curCanvas.height;                pdf.addImage(pageData, 'JPEG', leftMargin, topMargin, imgWidth, ratioHeight);            }else{                pdf.addImage(pageData, 'JPEG', leftMargin, topMargin, imgWidth, imgHeight);            }            if(i < (canvasArr.length-1)){                pdf.addPage();            }        }        let date = new Date();        let year = date.getFullYear();        let month = date.getMonth() + 1;        let day = date.getDate();        let milliSeconds = date.getMilliseconds();        pdf.save(year + month + day + milliSeconds +'.pdf');    }