HTML5画：线、圆、矩形、渐变

示例一：矩形

<!DOCTYPE html><head> 
<meta charset=utf-8> 
<title>HTML5画线、圆、矩形</title>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
</head> 
<script>
$(document).ready(function(){
var c=document.getElementById("drawbox");
var draw=c.getContext("2d");        //获取2d内容的引用，调用绘图API
draw.fillStyle="#ff0000";            //方式一指定填充颜色
draw.fillRect(0,0,300,100);            //坐标和长宽
draw.fillStyle="rgba(0,0,255,0.5)";    //方式二rgb+透明度
draw.fillRect(400,0,100,100);        //坐标和长宽
})
</script>
</body>
<canvas id="drawbox" width="500" height="500"></canvas>
</body> 
</html>

示例二：线

<!DOCTYPE html><head> 
<meta charset=utf-8> 
<title>HTML5画线、圆、矩形</title>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
</head> 
<script>
$(document).ready(function(){
var c=document.getElementById("drawbox");
var draw=c.getContext("2d");        //获取2d内容的引用，调用绘图API

draw.strokeStyle="#000000";　　//指定绘图线颜色
draw.moveTo(10,10);        //起始位置
draw.lineTo(150,10);    //终止位置
draw.lineTo(10,50);        //结束前继续之前的结束点连接
draw.lineTo(10,50);
draw.lineTo(10,10);
draw.stroke();            //结束
})
</script>
</body>
<canvas id="drawbox" width="500" height="500"></canvas>
</body> 
</html>

示例三：圆

<!DOCTYPE html><head> 
<meta charset=utf-8> 
<title>HTML5画线、圆、矩形</title>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
</head> 
<script>
$(document).ready(function(){
var c=document.getElementById("drawbox");
var draw=c.getContext("2d");            //获取2d内容的引用，调用绘图API

draw.fillStyle="red";                    //颜色
draw.beginPath();                        //从新画
draw.arc(50,50,50,0,Math.PI*2,true);     //圆心x坐标|圆心y坐标|直径|始|PI为圆周率，Math.PI*2为画圆|true为时针方向：逆时针，0为顺时针，
draw.closePath();                        //结束
draw.fill();
})
</script>
</body>
<canvas id="drawbox" width="500" height="500"></canvas>
</body> 
</html>

示例四：渐变

<!DOCTYPE html><head> 
<meta charset=utf-8> 
<title>HTML5画线、圆、矩形</title>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
</head> 
<script>
$(document).ready(function(){
var c=document.getElementById("drawbox");
var draw=c.getContext("2d");        //获取2d内容的引用，调用绘图API

//指定渐变区块
var grd=draw.createLinearGradient(50,50,200,50); //坐标，长宽
grd.addColorStop(0,"black");  //起点颜色
grd.addColorStop(1,"green");        //终点颜色

draw.fillStyle=grd;                //设为填充样式
draw.fillRect(50,50,200,50);    //填充进矩形内
})
</script>
</body>
<canvas id="drawbox" width="500" height="500"></canvas>
</body> 
</html>

HTML5 Canvas 画：线、圆、矩形、渐变

HTML5画：线、圆、矩形、渐变

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