基于JavaScript canvas绘制贝塞尔曲线

    
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 /** * Created by Administrator on 2017/8/11. * js/max.js */ (function () { var curEle = null; var startPointView = document.querySelector(".startPoint"); var endPointPointView = document.querySelector(".endPoint"); var point1View = document.querySelector(".point1"); var point2View = document.querySelector(".point2"); var context = null; function init() { var canvasEle = document.querySelector("#box"); canvasEle.width = innerWidth; canvasEle.height = innerHeight; //实时监听网页大小 window.onresize = function () { canvasEle.width = innerWidth; canvasEle.height = innerHeight; }; context = canvasEle.getContext("2d"); context.strokeStyle = "white"; context.lineWidth = 10; //贝塞尔曲线简单用法 context.beginPath(); context.moveTo(300,300); context.bezierCurveTo(500,200,600,250,600,600); context.stroke(); //循环获取四个点的数组 for(var i=0;i<4;i++){ addEvent([startPointView,endPointPointView,point1View,point2View][i]); } //鼠标双击移除鼠标滑动事件 放下拖动的点 document.ondblclick = function () { document.removeEventListener("mousemove",move); }; } //鼠标按下拖动 function addEvent(ele) { ele.onmousedown = function () { curEle = this; document.addEventListener("mousemove",move); }; } //获取拖动位置并绘制贝塞尔曲线 function move(event) { curEle.style.left = event.pageX+"px"; curEle.style.top = event.pageY+"px"; context.clearRect(0,0,innerWidth,innerHeight); context.beginPath(); context.moveTo(getLeft(startPointView),getTop(startPointView)); context.bezierCurveTo(getLeft(point1View),getTop(point1View),getLeft(point2View),getTop(point2View),getLeft(endPointPointView),getTop(endPointPointView)); context.stroke(); } function getLeft(ele) { return parseInt(ele.style.left); } function getTop(ele) { return parseInt(ele.style.top); } init(); })();