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HTML5 Canvas ( 贝塞尔曲线, 一片星空加绿地 ) quadraticCurveTo, bezierCurveTo

2017-03-29 22:54 441 查看 
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>canvas</title>
<script type="text/javascript" src="../js/jQuery.js"></script>
<style type="text/css">
*{
margin: 0;
padding: 0;
outline: none;
border: none;
}
#canvas{
width: 7rem;
margin: .25rem 0 0 1.5rem;
border: 1px solid black;
}
</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');

/**
* 贝塞尔二次曲线
* quadraticCurveTo(控制点的横坐标, 控制点的纵坐标, 曲线终点的横坐标, 曲线终点的纵坐标)
* 贝塞尔三次曲线
* bezierCurveTo(第一个控制点横坐标, 第一个控制点纵坐标, 第二个控制点横坐标, 第二个控制点纵坐标, 终点横坐标, 终点纵坐标)
*/

cxt.moveTo(300, 200);
//cxt.quadraticCurveTo(200, 200, 100, 300);
cxt.bezierCurveTo(400, 300, 200, 400, 300, 500);
cxt.strokeStyle = 'red';
cxt.lineWidth = 5;
cxt.stroke();
</script>


<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>canvas</title>
<script type="text/javascript" src="../js/jQuery.js"></script>
<style type="text/css">
*{
margin: 0;
padding: 0;
outline: none;
border: none;
}
#canvas{
width: 7rem;
margin: .25rem 0 0 1.5rem;
border: 1px solid black;
}
</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');

/**
* 绘制一片星空
*/
var skyStyle = cxt.createRadialGradient(canvas.width/2, canvas.height, 0, canvas.width/2, canvas.height, canvas.height);
skyStyle.addColorStop(0.0, '#035');
skyStyle.addColorStop(1.0, 'black');
cxt.fillStyle = skyStyle;

cxt.fillRect(0, 0, canvas.width, canvas.height);
for(var i = 0; i < 150; i++){
var fiveStart = {};
fiveStart.Radius = Math.random()*4+4;
fiveStart.offsetX = Math.random()*canvas.width;
fiveStart.offsetY = Math.random()*canvas.height*0.65;
fiveStart.RotationAngle = Math.random()*360;

drawFiveStar(cxt, fiveStart);
}
fillMoon(cxt, 1, 800, 150, 80, 30);
drawLand(cxt);

/**
* 绘制一片绿地
*/
function drawLand(cxt){
cxt.save();
cxt.beginPath();

cxt.moveTo(0, 500);
cxt.bezierCurveTo(540, 300, 660, 600, 1200, 500);
cxt.lineTo(1200, 600);
cxt.lineTo(0, 600);

var LandStyle =  cxt.createLinearGradient(0, 800, 0, 0);
LandStyle.addColorStop(0.0, "#030");
LandStyle.addColorStop(1.0, '#580');
cxt.fillStyle = LandStyle;
cxt.closePath();
cxt.fill();
cxt.restore();
}

/**
* 绘制月亮的方法
*/
function fillMoon(cxt, d, x, y, R, rot){
cxt.save();
cxt.translate(x, y);
cxt.rotate(rot*Math.PI/180);
cxt.scale(R, R);
pathMoon(cxt, d);
cxt.fillStyle = 'yellow';
cxt.fill();
cxt.restore();
}
function pathMoon(cxt, d){
cxt.beginPath();
cxt.arc(0, 0, 1, 0.5*Math.PI, 1.5*Math.PI, true);
cxt.moveTo(0, -1);
cxt.arcTo(d, 0, 0, 1, dis(0, -1, d, 0)/d);
cxt.closePath();
}

function dis(x1, y1, x2, y2){
return Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
}

/**
* 控制五角星的方法
*/
function drawFiveStar(cxt, fiveStart){
cxt.save();
cxt.translate(fiveStart.offsetX, fiveStart.offsetY); //相对于原点的偏移量
cxt.rotate(fiveStart.RotationAngle/180*Math.PI); //图形旋转(弧度)
cxt.scale(fiveStart.Radius, fiveStart.Radius); //图形缩放( X轴的倍数, Y轴的倍数 )
fiveStartPath(cxt);
cxt.fillStyle = "yellow";
cxt.fill();
cxt.restore();
}
function fiveStartPath(cxt){
cxt.beginPath();
var x = 0; y = 0;
for(var i = 0; i < 5; i++){
x = Math.cos((18+72*i)/180*Math.PI);
y = Math.sin((18+72*i)/180*Math.PI);
cxt.lineTo(x, 0-y);
x = Math.cos((54+72*i)/180*Math.PI)/2.0;
y = Math.sin((54+72*i)/180*Math.PI)/2.0;
cxt.lineTo(x, 0-y);
}
cxt.closePath();
}
</script>
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