PDF Viewer Builder creates a p…

# 本地PDF查看器（单文件，直接保存为 .html 使用）

使用方法

将下面代码保存为 pdf-viewer.html，双击用浏览器打开即可。

```html

<!DOCTYPE html>

<html lang="zh">

<head>

<meta charset="UTF-8">

<title>PDF查看器</title>

<script src="https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.min.js"></script>

<style>

body{font-family:sans-serif;background:#f0f0f0;margin:0;padding:20px;text-align:center}

#toolbar{background:#fff;padding:10px;border-radius:8px;box-shadow:0 2px 6px rgba(0,0,0,.15);display:inline-flex;gap:10px;align-items:center;margin-bottom:15px}

canvas{background:#fff;box-shadow:0 2px 10px rgba(0,0,0,.2);max-width:95vw}

button{padding:6px 14px;cursor:pointer}

input[type=number]{width:60px;padding:6px}

#pageInfo{min-width:90px;display:inline-block}

</style>

</head>

<body>

<div id="toolbar">

<input type="file" id="fileInput" accept="application/pdf">

<button id="prevBtn" disabled>◀ 上一页</button>

<input type="number" id="pageJump" min="1" value="1">

<span id="pageInfo">/ 0</span>

<button id="nextBtn" disabled>下一页 ▶</button>

<button id="zoomOut">－</button>

<span id="zoomLabel">100%</span>

<button id="zoomIn">＋</button>

<button id="downloadBtn" disabled>下载当前页PNG</button>

</div>

<br><canvas id="canvas"></canvas>

<script>

pdfjsLib.GlobalWorkerOptions.workerSrc='https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.worker.min.js';

let pdf=null, pageNum=1, scale=1.0; // 缩放范围0.5~3.0

const canvas=document.getElementById('canvas'), ctx=canvas.getContext('2d');

document.getElementById('fileInput').addEventListener('change', e=>{

const file=e.target.files[0]; if(!file) return;

const reader=n