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

2024-09-11 07:02:56   217人阅读

<!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>

 

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


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