如何抓取画布标签?为什么它在我的浏览器中不可见？

// 获取canvas元素
var canvas = document.getElementById('myCanvas');
// 获取2D绘图上下文
var ctx = canvas.getContext('2d');
// 获取图像数据
var imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);

// 获取canvas元素
var canvas = document.getElementById('myCanvas');
// 将canvas内容转换为PNG格式的数据URL
var dataURL = canvas.toDataURL('image/png');

/* 错误的样式 */
#myCanvas {
    display: none;
}

/* 正确的样式 */
#myCanvas {
    display: block;
    width: 100%;
    height: auto;
}

<canvas id="myCanvas" width="640" height="480"></canvas>

var canvas = document.getElementById('myCanvas');
var ctx = canvas.getContext('2d');
ctx.fillStyle = 'green';
ctx.fillRect(10, 10, 100, 100);

var img = new Image();
img.crossOrigin = "Anonymous";
img.src = "https://example.com/image.png";
img.onload = function() {
    var canvas = document.getElementById('myCanvas');
    var ctx = canvas.getContext('2d');
    ctx.drawImage(img, 0, 0);
};