html5学习笔记二

html5 音频
audio支持的三种音频格式：
Ogg Vorbis
MP3
Wav
示例代码如下：
<audio controls="controls">
<source src="" type="audio/ogg">
<source src="" type="audio/mpeg">
错误信息显示
</audio>
常用属性：
autoplay: 音频就绪后马上播放
control: 添加播放，暂停和音量控件
loop: 是否重复播放
preload: 音频在音乐加载时进行加载
src: 音频播放路径



html5 canvas
canvas 使用javascript在网页上绘制图像 (可以指定画布大小)
示例代码如下：
<canvas id="myCanvas" width="200" height="100"></canvas>
canvas 元素本身是没有绘图能力，所有绘制工作必须在javascript内完成

<script type="text/javascript">
var c=document.getElementById("myCanvas");
var cxt=c.getContext("2d");
cxt.fillStyle="#FF0000";
cxt.fillRect(0,0,150,75);
</script>
绘制一条直线
<canvas id="myCanvas2" width="200" height="100" style="border:1px solid #c3c3c3;">
Your browser does not support the canvas element.
</canvas>


<script type="text/javascript">
var c=document.getElementById("myCanvas2");
var cxt=c.getContext("2d");
cxt.moveTo(10,10);
cxt.lineTo(150,50);
cxt.lineTo(10,50);
cxt.stroke();
</script>

绘制圆形
<canvas id="myCanvas3" width="200" height="100" style="border:1px solid #c3c3c3;">
错误信息
</canvas>
<script type="text/javascript">
var c=document.getElementById("myCanvas");
var cxt=c.getContext("2d");
cxt.fillStyle="#FF0000";
cxt.beginPath();
cxt.arc(70,18,15,0,Math.PI*2,true);
cxt.closePath();
cxt.fill();
</script>

绘制渐变
<canvas id="myCanvas4" width="200" height="100" style="border:1px solid #c3c3;">
</canvas>
<script type="text/javascript">
var c=document.getElementById("myCanvas4");
var cxt=c.getContext("2d");
var grd=cxt.createLinearGradient(0,0,175,50);
grd.addColorStop(0,"#FF0000");
grd.addColorStop(1,"#00FF00");
cxt.fillStyle=grd;
cxt.fillRect(0,0,175,50);
</script>

放置一副图片
<canvas id="myCanvas5" width="200" height="100" style="border:1px solid #c3c3c3">
</canvas>
<script type="text/javascript">
var c=document.getElementById("myCanvas5");
var cxt=c.getContext("2d");
var img=new Image();
img.src="图片名";
cxt.drawImage(img,0,0);
</script>