html5 利用canvas手写签名并保存的实现方法canvas画布实现手写签名效果的示例代码如何用canvas实现在线签名的示例代码Html5基于canvas实现电子签名并生成PDF文档

 window.onload = function() { new lineCanvas({ el: document.getElementById("canvas"),//绘制canvas的父级div clearEl: document.getElementById("clearCanvas"),//清除按钮 saveEl: document.getElementById("saveCanvas"),//保存按钮 // linewidth:1,//线条粗细，选填 // color:"black",//线条颜色，选填 // background:"#ffffff"//线条背景，选填 }); }; function lineCanvas(obj) { this.linewidth = 1; this.color = "#000000"; this.background = "#ffffff"; for (var i in obj) { this[i] = obj[i]; }; this.canvas = document.createElement("canvas"); this.el.appendChild(this.canvas); this.cxt = this.canvas.getContext("2d"); this.canvas.width = this.el.clientWidth; this.canvas.height = this.el.clientHeight; this.cxt.fillStyle = this.background; this.cxt.fillRect(0, 0, this.canvas.width, this.canvas.width); this.cxt.strokeStyle = this.color; this.cxt.lineWidth = this.linewidth; this.cxt.lineCap = "round"; //开始绘制 this.canvas.addEventListener("touchstart", function(e) { this.cxt.beginPath(); this.cxt.moveTo(e.changedTouches[0].pageX, e.changedTouches[0].pageY); }.bind(this), false); //绘制中 this.canvas.addEventListener("touchmove", function(e) { this.cxt.lineTo(e.changedTouches[0].pageX, e.changedTouches[0].pageY); this.cxt.stroke(); }.bind(this), false); //结束绘制 this.canvas.addEventListener("touchend", function() { this.cxt.closePath(); }.bind(this), false); //清除画布 this.clearEl.addEventListener("click", function() { this.cxt.clearRect(0, 0, this.canvas.width, this.canvas.height); }.bind(this), false); //保存图片，直接转base64 this.saveEl.addEventListener("click", function() { var imgBase64 = this.canvas.toDataURL(); console.log(imgBase64); }.bind(this), false); }; 

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 html,body{ width: 100%; height: 100%; } #canvas{ width: 100%; height: 100%; position: relative; } #canvas canvas{ display: block; } #clearCanvas{ width: 50%; height: 40px; line-height: 40px; text-align: center; position: absolute; bottom: 0; left: 0; border: 1px solid #DEDEDE; z-index: 1; } #saveCanvas{ width: 50%; height: 40px; line-height: 40px; text-align: center; position: absolute; bottom: 0; right: 0; border: 1px solid #DEDEDE; z-index: 1; }