《JS原理、方法与实践》- canvas作图（八）- 阴影-CFANZ编程社区

属性值：

shadowOffsetX: 阴影的水平偏移距离
shadowOffsetY: 阴影的竖直偏移距离
shadowBlur: 阴影的模糊效果，数字越大越模糊
shadowColor: 阴影颜色

示例：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <canvas id="c2d">浏览器不支持canvas</canvas>
    <script>
        const canvas = document.querySelector('#c2d');
        if(canvas.getContext) {
            const ctx = canvas.getContext('2d');
            
            // 设置阴影效果
            ctx.shadowOffsetX = -7;
            ctx.shadowOffsetY = 5;
            ctx.shadowBlur = 3;
            ctx.shadowColor = 'rgba(255,255,0,0.7)';
            
            ctx.fillStyle = 'red';
            ctx.fillRect(15,30,130,40);
        }
    </script>

</body>
</html>