canvas仿写贝塞尔曲线的示例代码

天正在等烟雨，而我在等你，啦啦啦，欢迎关注我的简书，今天分享的是原创的canvas仿写贝塞尔曲线方法。具体如下：

效果图：

html

<canvas id="mycanvas" width="500" height="500">您的浏览器不支持canvas</canvas>

css

canvas{ border: 1px solid black;}

js

var canvas = document.getelementbyid("mycanvas");
        var context = canvas.getcontext("2d");
        var x1 = 100;
        var y1 = 100;
        var x2 = 400;
        var y2 = 400;
        draw();
        function draw(){
            //画半透明的线
            context.beginpath();
            context.moveto(500,0);
            context.lineto(0,500);
            context.strokestyle = "rgba(0,0,0,0.3)";
            context.linewidth = 10;
            context.stroke();
            //画连接线
            context.beginpath();
            context.moveto(0,500);
            context.lineto(x1,y1);
            context.linewidth = 2;
            context.strokestyle = "black";
            context.stroke();
            context.beginpath();
            context.moveto(500,0);
            context.lineto(x2,y2);
            context.linewidth = 2;
            context.strokestyle = "black";
            context.stroke();
            //画红球
            context.beginpath();
            context.arc(x1,y1,10,0,math.pi*2);
            context.fillstyle = "orange";
            context.fill();
            //画蓝球
            context.beginpath();
            context.arc(x2,y2,10,0,math.pi*2);
            context.fillstyle = "blue";
            context.fill();
            //画贝塞尔曲线
            context.beginpath();
            context.moveto(0,500);
            context.beziercurveto(x1,y1,x2,y2,500,0);
            context.linewidth = 5;
            context.stroke();
        }
        //拖动小球做动画
        //判断是否拖动小球
        //如果在小球上就做动画
        canvas.onmousedown = function(e){
            var ev = e || window.event;
            var x = ev.offsetx;
            var y = ev.offsety;
            //判断是否在红球上
            var dis = math.pow((x-x1),2) + math.pow((y-y1),2);
            if(dis<100){
                console.log("鼠标在红球上");
                canvas.onmousemove = function(e){
                    var ev = e || window.event;
                    var xx = ev.offsetx;
                    var yy = ev.offsety;
                    //清除画布
                    context.clearrect(0,0,canvas.width,canvas.height);
                    x1 = xx;
                    y1 = yy;
                    //重绘制
                    draw();
                }
            }
            //判断鼠标是否在蓝球上
            var dis = math.pow((x-x2),2) + math.pow((y-y2),2);
            if(dis<100){
                canvas.onmousemove = function(e){
                    var ev = e || window.event;
                    var xx1 = ev.offsetx;
                    var yy1 = ev.offsety;
                    //清除画布
                    context.clearrect(0,0,canvas.width,canvas.height);
                    x2 = xx1;
                    y2 = yy1;
                    //重绘制
                    draw();
                }
            }
        }
        document.onmouseup =function(){
            canvas.onmousemove = " ";
        }

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