canvas基础

Posted 2020-10-02 我哼哼-爱前端

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1.画直线

1 context.beginPath();
2 context.moveTo(100, 100);
3 context.lineTo(700, 700);
4 context.lineTo(100, 700);
5 context.lineTo(100, 100);
6 context.closePath();
7 context.lineWidth = 5;
8 context.strokeStyle = "#005588";
9 context.stroke();

2.画圓弧

context.lineWidth = 5;
context.strokeStyle = "#005588";
for(var i = 0;i<10;i++){
context.beginPath();	
context.arc(50 + i*100,60,40,0,2*Math.PI*(i+1)/10);
context.closePath();
context.stroke();
}
for(var i = 0;i<10;i++){
context.beginPath()	
context.arc(50 + i*100,180,40,0,2*Math.PI*(i+1)/10);
context.stroke();
}

3.画七巧板

html部分

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8" />
		<title></title>
	</head>

	<body>
		<!--width="1024" height="786"-->
		<canvas id="canvas" style=" border:1px solid #aaa;display: block;margin: 50px auto;">
			<!--当前浏览器不支持canvas,请更换浏览器后再试-->
		</canvas>
	</body>
</html>

javascript部分

var tangram = [
{p:[{x:0,y:0},{x:800,y:0},{x:400,y:400}],color:"#caff67"},
{p:[{x:0,y:0},{x:400,y:400},{x:0,y:800}],color:"#67becf"},
{p:[{x:800,y:0},{x:800,y:400},{x:600,y:600},{x:600,y:200}],color:"#ef3d61"},
{p:[{x:600,y:200},{x:600,y:600},{x:400,y:400}],color:"#f9f51a"},
{p:[{x:400,y:400},{x:600,y:600},{x:400,y:800},{x:200,y:600}],color:"#a594c0"},
{p:[{x:200,y:600},{x:400,y:800},{x:0,y:800}],color:"#fa8ecc"},
{p:[{x:800,y:400},{x:800,y:800},{x:400,y:800}],color:"#f6ca29"}
]
		window.onload = function() {
			var canvas = document.getElementById(‘canvas‘);
			//设置画布的宽和高
			canvas.width = 800;
			canvas.height = 800;

			//判断浏览器是否支持canvas
			if(canvas.getContext(‘2d‘)) {
				var context = canvas.getContext("2d");
				//使用context绘制
			} else {
				alert("当前浏览器不支持canvas,请更换浏览器后再试");
			}
			
			for(var i = 0;i<tangram.length;i++){
				draw(tangram[i],context);
			}
		}
		function draw(piece,cxt){
			cxt.beginPath();
			cxt.moveTo(piece.p[0].x,piece.p[0].y);
			for(var i =1;i<piece.p.length;i++){
				cxt.lineTo(piece.p[i].x,piece.p[i].y);
				
			}
			cxt.closePath();
			
			cxt.fillStyle = piece.color;
			cxt.fill();
			
			cxt.strokeStyle = "black";
			cxt.lineWidth = 3;
			cxt.stroke();
		}

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