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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" />
<title>Dynamic Canvas Watermark</title>
<link rel="stylesheet" href="./src/styles.css" />
<style>
.watermarked-content {
position: relative;
width: 100vw;
height: 100vh;
background-color: #f5f5f5;
overflow: hidden;
}
.inner-content {
display: flex;
align-items: center;
justify-content: center;
width: 100%;
height: 100%;
z-index: 900;
}
.watermark-canvas {
position: absolute;
top: 0px;
left: 0px;
transform-origin: center center;
}
</style>
</head>
<body>
<nav>
<a href="/" aria-current="page">Home</a>
<a href="/page-1.html">加码</a>
<a href="/page-2.html">解码</a>
<a href="/page-3.html">提取内容</a>
</nav>
<div id="targetElement" class="watermarked-content">
<div class="inner-content">
<span>Your content goes here.</span>
</div>
</div>
<script>
// 创建或重新创建水印 Canvas
function createWatermarkCanvas(
text = 'user name',
spacing = 80,
opacity = 0.1,
angle = -30
) {
const container = document.querySelector('.watermarked-content');
let canvas = document.querySelector('.watermark-canvas');
if (!canvas) {
canvas = document.createElement('canvas');
canvas.className = 'watermark-canvas';
container.appendChild(canvas);
}
const ctx = canvas.getContext('2d');
const rad = angle * (Math.PI / 180);
const fontSize = 20;
// const canvasWidth = container.offsetWidth;
// const canvasHeight = container.offsetHeight;
const width = container.offsetWidth;
const height = container.offsetHeight;
const newWidth =
Math.abs(width * Math.cos(rad)) + Math.abs(height * Math.sin(rad));
const newHeight =
Math.abs(height * Math.cos(rad)) + Math.abs(width * Math.sin(rad));
const canvasWidth = newWidth;
const canvasHeight = newHeight;
const textWidth = ctx.measureText(text).width;
const textHeight = fontSize; // Approximation
canvas.width = canvasWidth;
canvas.height = canvasHeight;
// 调整 canvas 的位置
canvas.style.position = 'absolute';
canvas.style.top = `-${(newHeight - height) / 2}px`;
canvas.style.left = `-${(newWidth - width) / 2}px`;
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.font = `${fontSize}px Arial`;
ctx.fillStyle = `rgba(0, 0, 0, ${opacity})`;
ctx.textAlign = 'center';
ctx.textBaseline = 'middle';
// Calculate the number of text repetitions needed for width and height
const numRows = Math.ceil(canvasHeight / (textHeight + spacing));
const numCols = Math.ceil(canvasWidth / (textWidth + spacing));
ctx.save();
ctx.translate(canvasWidth / 2, canvasHeight / 2);
ctx.rotate(rad); // Rotate text if needed
// Draw repeated text with spacing
for (let row = 0; row < numRows; row++) {
for (let col = 0; col < numCols; col++) {
const x = col * (textWidth + spacing) - canvasWidth / 2;
const y = row * (textHeight + spacing) - canvasHeight / 2;
ctx.fillText(text, x, y);
}
}
ctx.restore();
}
// 确保 Canvas 始终位于最上层
function ensureCanvasOnTop(defaultMaxZIndex = 1000) {
const canvas = document.querySelector('.watermark-canvas');
if (canvas) {
// 获取所有元素的最高 z-index
let maxZIndex = Array.from(document.querySelectorAll('body *'))
.map((el) => parseFloat(window.getComputedStyle(el).zIndex))
.filter((zIndex) => !isNaN(zIndex))
.reduce((max, zIndex) => Math.max(max, zIndex), defaultMaxZIndex);
// 只有在发现新的最大 z-index 超过默认值时，才更新 canvas 的 z-index
if (maxZIndex >= defaultMaxZIndex) {
canvas.style.zIndex = maxZIndex + 1;
}
}
}
// 确保 Canvas 始终可见
function ensureCanvasVisibility() {
const canvas = document.querySelector('.watermark-canvas');
if (canvas) {
const style = window.getComputedStyle(canvas);
// 确保 Canvas 始终可见
if (
style.display === 'none' ||
style.visibility === 'hidden' ||
parseFloat(style.opacity) === 0
) {
canvas.style.display = 'block';
canvas.style.visibility = 'visible';
canvas.style.opacity = 1;
createWatermarkCanvas(); // 重新绘制水印
}
}
}
// 设置 MutationObserver
function setupObservers() {
const targetNode = document.querySelector('.watermarked-content');
const canvas = document.querySelector('.watermark-canvas');
if (targetNode) {
const observer = new MutationObserver((mutations) => {
mutations.forEach((mutation) => {
// 监听属性变动
if (
mutation.type === 'attributes' &&
mutation.attributeName === 'style'
) {
ensureCanvasVisibility();
}
// 监听 DOM 变动
ensureCanvasOnTop();
createWatermarkCanvas();
});
});
// 监听水印容器的子元素、属性变化
observer.observe(targetNode, {
attributes: true,
childList: true,
subtree: true,
});
}
// 监听 Canvas 内容变动
if (canvas) {
const canvasObserver = new MutationObserver(() => {
createWatermarkCanvas();
});
canvasObserver.observe(canvas, { childList: true, subtree: true });
}
}
// 初始化函数
function initializeWatermark() {
createWatermarkCanvas();
ensureCanvasOnTop();
setupObservers();
}
window.onload = initializeWatermark;
</script>
</body>
</html>