天正在等煙雨，而我在等你，啦啦啦，歡迎關(guān)注我的簡(jiǎn)書(shū)，今天分享的是原創(chuàng)的canvas仿寫(xiě)貝塞爾曲線方法。具體如下：
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(){
//畫(huà)半透明的線
context.beginPath();
context.moveTo(500,0);
context.lineTo(0,500);
context.strokeStyle = "rgba(0,0,0,0.3)";
context.lineWidth = 10;
context.stroke();
//畫(huà)連接線
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();
//畫(huà)紅球
context.beginPath();
context.arc(x1,y1,10,0,Math.PI*2);
context.fillStyle = "orange";
context.fill();
//畫(huà)藍(lán)球
context.beginPath();
context.arc(x2,y2,10,0,Math.PI*2);
context.fillStyle = "blue";
context.fill();
//畫(huà)貝塞爾曲線
context.beginPath();
context.moveTo(0,500);
context.bezierCurveTo(x1,y1,x2,y2,500,0);
context.lineWidth = 5;
context.stroke();
}
//拖動(dòng)小球做動(dòng)畫(huà)
//判斷是否拖動(dòng)小球
//如果在小球上就做動(dòng)畫(huà)
canvas.onmousedown = function(e){
var ev = e || window.event;
var x = ev.offsetX;
var y = ev.offsetY;
//判斷是否在紅球上
var dis = Math.pow((x-x1),2) + Math.pow((y-y1),2);
if(dis<100){
console.log("鼠標(biāo)在紅球上");
canvas.onmousemove = function(e){
var ev = e || window.event;
var xx = ev.offsetX;
var yy = ev.offsetY;
//清除畫(huà)布
context.clearRect(0,0,canvas.width,canvas.height);
x1 = xx;
y1 = yy;
//重繪制
draw();
}
}
//判斷鼠標(biāo)是否在藍(lán)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;
//清除畫(huà)布
context.clearRect(0,0,canvas.width,canvas.height);
x2 = xx1;
y2 = yy1;
//重繪制
draw();
}
}
}
document.onmouseup =function(){
canvas.onmousemove = " ";
}
