<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>canvas</title>
<script type="text/javascript" src="../js/jQuery.js"></script>
<style type="text/css">
#canvas{
width: 7rem;
margin: .25rem 0 0 1.5rem;
border: 1px solid black;
display: block;
}
</style>
</head>
<body>
<canvas id="canvas" width="1000" height="600"></canvas>
</body>
</html>
<script type="text/javascript">
/**
* rem 布局初始化
*/
$('html').css('font-size', $(window).width()/10);
/**
* 获取 canvas 画布
* 获取 canvas 绘图上下文环境
*/
var canvas = $('#canvas')[0];
var cxt = canvas.getContext('2d');
var balls = [];
/**
* 事件交互, 点击事件为例
* isPointInPath(横坐标, 纵坐标)
*/
for(var i = 0; i < 10; i++){
var ball = {
X: Math.random()*canvas.width,
Y: Math.random()*canvas.height,
R: Math.random()*50 + 20
}
balls[i] = ball;
}
draw();
$("#canvas").click(function(){
//标准的获取鼠标点击相对于canvas画布的坐标公式
var x = event.pageX - canvas.getBoundingClientRect().left;
var y = event.pageY - canvas.getBoundingClientRect().top;
for(var i = 0; i < balls.length; i++){
cxt.beginPath();
cxt.arc(balls[i].X, balls[i].Y, balls[i].R, 0, Math.PI*2);
if(cxt.isPointInPath(x, y)){
cxt.fillStyle = "red";
cxt.fill();
}
}
});
function draw(){
cxt.fillStyle = "blue";
for(var i = 0; i < balls.length; i++){
cxt.beginPath();
cxt.arc(balls[i].X, balls[i].Y, balls[i].R, 0, Math.PI*2);
cxt.fill();
}
}
</script>
