学习html5canvas画图

发布时间：2020-07-18 09:52:12 作者：haotianaoxiang
来源：网络阅读：354

1.得到一个canvas元素 2.用canvas元素去得到一个html5内置内置的工具getContext("2d")

3.常用的方法，fillStyle属性指明填充的颜色样式，fillRect(x,y,width,height)画矩形

4.画直线moveTo(x,y) lineTo(x,y) closePath() stroke() 属性：lineJoin 默认是平角round是圆角 lineCap有3个值：butt（平，默认）,round（圆）,square（方） lineWidth线条宽度 stokeStyle线条的颜色样式学习http://www.jb51.net/html5/70307.html

5画圆形cxt2.arc(100,100,100,0,Math.PI*2,true);cxt2.closePath();cxt2.fill();

arc（x,y,r,0,Math.PI*2,true）x，y圆心 r半径

6.渐变填充

var grd=cxt3.createLinearGradient(0,0,180,100);grd.addColorStop(0,"#FF0000");

grd.addColorStop(1,"#00FF00");cxt3.fillStyle=grd;cxt3.fillRect(0,0,180,100);

addColorStop(x,color) 0=《x《=1 开始和技术时的颜色

7.图像填充var can4 = document.getElementById('can4');

var cxt4 = can4.getContext("2d");

var img = new Image();

img.src ="22.gif";

console.log(img);

cxt4.drawImage(img,0,0);这样的结果并不会显示出来图像

因为img没有加载进来，解决办法img.onload = function () {

cxt4.drawImage(img, 50, 50,100,100);

}

代码：1.html

<style>

#can1{border:solid 1px blue;}

</style>

</head>

<body>

var can1 = document.getElementById('can1');

var cxt = can1.getContext("2d");

cxt.fillStyle="blue";

cxt.fillRect(0,0,50,50);

cxt.moveTo(60,60);

cxt.lineTo(150,60);

//cxt.moveTo(150,60);

cxt.lineTo(150,150);

cxt.lineTo(60,150);

cxt.lineTo(60,60);

//cxt.lineJoin="round";

//cxt.closePath();

cxt.lineCap="square";

cxt.lineWidth=20;

cxt.strokeStyle = 'rgba(255,0,0,0.5)';

cxt.stroke();

</script>

代码2.html

var can2 = document.getElementById('can2');

var cxt2 = can2.getContext("2d");

cxt2.fillStyle="#FF0000";

cxt2.arc(100,100,100,0,Math.PI*2,true);

cxt2.closePath();

cxt2.fill();

var can3 = document.getElementById('can3');

var cxt3 = can3.getContext("2d");

var grd=cxt3.createLinearGradient(0,0,180,100);

grd.addColorStop(0,"#FF0000");

grd.addColorStop(1,"#00FF00");

cxt3.fillStyle=grd;

cxt3.fillRect(0,0,180,100);

var can4 = document.getElementById('can4');