基于JavaScript canvas绘制贝塞尔曲线
程序员文章站
2022-07-02 21:42:35
简单描述：页面上有四个点，鼠标拖动四个点的位置来改变贝塞尔曲线的形状，双击放置点位
效果图：
代码：
...
简单描述：页面上有四个点，鼠标拖动四个点的位置来改变贝塞尔曲线的形状，双击放置点位
效果图：
代码：
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>title</title>
<style>
html{overflow: hidden;}
* {padding: 0;margin: 0;}
#box {background-color: #000000;}
.point {
width: 20px;
height: 20px;
background-color: #fff;
border-radius: 50%;
position: absolute;
left: 100px;
top:200px;
text-align: center;
line-height: 20px;
}
</style>
</head>
<body>
<canvas id="box"></canvas>
<div class="point startpoint">b</div>
<div class="point endpoint">e</div>
<div class="point point1">1</div>
<div class="point point2">2</div>
<script src="js/max.js"></script>
</body>
</html>
js：
/**
* 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();
})();
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