canvas-learning/drawLineJoin.html at master · luogao/canvas-learning · GitHub

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<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Canvas学习-画线</title>
    <style>
        html,
        body {
            height: 100%;
            margin: 0;
        }

        canvas {
            display: block;
        }
    </style>
</head>

<body>
    <canvas id="canvas">
        <p>你的浏览器不支持Canvas</p>
    </canvas>
    <script>
        function canvasApp() {
            var canvas = document.getElementById("canvas");
            canvas.height = window.innerHeight
            canvas.width = window.innerWidth
            var ctx = canvas.getContext('2d');
            var w = canvas.width;
            var h = canvas.height;
            ctx.clearRect(0, 0, w, h);

            function drawScreen() {
                ctx.font = "24px Arial"
                ctx.strokeStyle = "#f9f"
                ctx.lineWidth = 30

                ctx.beginPath()
                ctx.lineJoin = "miter"
                ctx.moveTo(30, 50)
                ctx.lineTo(120, 50)
                ctx.lineTo(120, 280)
                ctx.fillText('miter 斜切', 30, 20)
                ctx.lineCap = 'square';
                ctx.stroke()

                ctx.beginPath()
                ctx.lineJoin = 'round'
                ctx.moveTo(180, 50)
                ctx.lineTo(280, 50)
                ctx.lineTo(280, 280)
                ctx.lineTo(180, 280)
                ctx.fillText('round 圆角', 180, 20)
                ctx.stroke()

                ctx.beginPath()
                ctx.lineJoin = 'bevel'
                ctx.moveTo(350, 50)
                ctx.lineTo(450, 50)
                ctx.lineTo(450, 280)
                ctx.lineTo(350, 280)
                ctx.fillText('bevel 斜角', 350, 20)
                ctx.stroke()


                ctx.strokeStyle = "red"
                ctx.lineWidth = 5
                ctx.beginPath()
                ctx.lineJoin = 'miter'
                for (var i = 0; i < 5; i++) {
                    ctx.lineTo(Math.cos((18 + 72 * i) / 180 * Math.PI) * 100 + 200, -Math.sin((18 + 72 * i) / 180 * Math.PI) * 100 + 120)
                    ctx.lineTo(Math.cos((54 + 72 * i) / 180 * Math.PI) * 50 + 200, -Math.sin((54 + 72 * i) / 180 * Math.PI) * 50 + 120)
                }
                ctx.closePath()
                ctx.stroke()
            }
            drawScreen()
        }

        function eventWindowLoaded() {
            canvasApp()
        }

        window.addEventListener('load', eventWindowLoaded, false)
        window.addEventListener('resize', eventWindowLoaded, false)
    </script>
</body>

</html>