扣丁学堂HTML5在线教程之canvas仿写贝塞尔曲线的示例代码

2018-06-07 13:52:12 524浏览

本篇文章扣丁学堂HTML5培训小编主要是和大家分享一下canvas仿写贝塞尔曲线的示例，文章中会有代码列出供大家详细了解。对HTML5感兴趣想要学好HTML5开发技术的小伙伴们随着小编一起来看一下吧。

代码如下：

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 = " ";
        }

以上就是扣丁学堂HTML5在线学习小编给大家分享的canvas仿写贝塞尔曲线的示例代码，希望对小伙伴们有所帮助，想要了解更多内容的小伙伴可以登录扣丁学堂官网咨询。扣丁学堂是专业的HTML5培训机构，不仅有专业的老师和与时俱进的课程体系，还有大量的HTML5在线教程供学员观看学习，喜欢HTML5的小伙伴快快行动吧。扣丁学堂H5技术交流群：559883758。  

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