canvas基础
1.画直线（基于状态（moveTo，lineTo）的绘制(stroke) moveTo lineTo stroke lineWidth strokeStyle 等这些方法 都基于canvas.getContext() 这个对象）
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 arc方法（arc（共6个参数 中心点的x，y值，半径r，开始角度，结束角度，是否顺逆时针））
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();
}
