我开始使用pdf.js库构建pdf查看器。我真的很喜欢其中一些示例的简单性，因此我使用PREV / NExt示例启动了我的查看器：
https://github.com/mozilla/pdf.js/blob/master/examples/learning/prevnext.html
我想添加放大和缩小，并找到了这个简单的查看器，我想对其进行建模并滚动到以下位置：
https://github.com/zedr/simple-pdf-reader.js/blob/master/viewer.js
这是我的index.html的html：
<div class="row">
<div class="col-md-4">
<button class="btn btn-primary" id="prev"><i class="fa fa-level-up fa-lg"></i></button>
<button class="btn btn-primary" id="next"><i class="fa fa-level-down fa-lg"></i></button>
</div><div class="col-md-4">
<span>Page: <span id="page_num"></span> / <span id="page_count"></span></span>
<div id="pdf-controls">
<button id="zoom_minus" onclick="url.zoomMinus()"
oncontextmenu="return false;" class="btn btn-primary">-</button>
<button id="zoom_plus" onclick="url.zoomPlus()"
oncontextmenu="return false;" class="btn btn-primary">+</button>
<div id="pdf-stats">
<p>
<span id="pdf-page-zoom">n/a</span> <span>%</span>
</p>
</div>
</div>
</div><div class="col-md-4 pull-right">
<a href="sample.pdf" class="btn btn-primary"><i class="fa fa-arrows-alt fa-lg"></i></a>
<a href="sample.pdf" class="btn btn-primary" download><i class="fa fa-cloud-download fa-lg"></i></a>
</div>
</div>
<br><br>
<center>
<div style="overflow: scroll" id="pdfviewer">
<canvas id="pdfcanvas" style="border:1px solid black; width: 100%"></canvas>
</div>
</center>
这是我的viewer.js的JavaScript：
<script id="pdfviewer">
//
// If absolute URL from the remote server is provided, configure the CORS
// header on that server.
//
var url = 'sample.pdf';
//
// Disable workers to avoid yet another cross-origin issue (workers need
// the URL of the script to be loaded, and dynamically loading a cross-origin
// script does not work).
//
// PDFJS.disableWorker = true;
//
// In cases when the pdf.worker.js is located at the different folder than the
// pdf.js's one, or the pdf.js is executed via eval(), the workerSrc property
// shall be specified.
//
PDFJS.workerSrc = 'pdf.worker.js';
var pdfDoc = null,
pageNum = 1,
pageRendering = false,
pageNumPending = null,
scale = 1.5,
canvas = document.getElementById('pdfcanvas'),
ctx = canvas.getContext('2d');
var camera = {
x: 0,
y: 0,
scale: 1,
};
/**
* Get page info from document, resize canvas accordingly, and render page.
* @param num Page number.
*/
function renderPage(num) {
pageRendering = true;
// Using promise to fetch the page
pdfDoc.getPage(num).then(function(page) {
var viewport = page.getViewport(scale);
canvas.height = viewport.height;
canvas.width = viewport.width;
// Render PDF page into canvas context
var renderContext = {
canvasContext: ctx,
viewport: viewport
};
var renderTask = page.render(renderContext);
// Wait for rendering to finish
renderTask.promise.then(function () {
pageRendering = false;
if (pageNumPending !== null) {
// New page rendering is pending
renderPage(pageNumPending);
pageNumPending = null;
}
});
});
// Update page counters
document.getElementById('page_num').textContent = pageNum;
}
/**
* If another page rendering in progress, waits until the rendering is
* finised. Otherwise, executes rendering immediately.
*/
function queueRenderPage(num) {
if (pageRendering) {
pageNumPending = num;
} else {
renderPage(num);
}
}
/**
* Displays previous page.
*/
function onPrevPage() {
if (pageNum <= 1) {
return;
}
pageNum--;
queueRenderPage(pageNum);
}
document.getElementById('prev').addEventListener('click', onPrevPage);
/**
* Displays next page.
*/
function onNextPage() {
if (pageNum >= pdfDoc.numPages) {
return;
}
pageNum++;
queueRenderPage(pageNum);
}
document.getElementById('next').addEventListener('click', onNextPage);
/**
* Asynchronously downloads PDF.
*/
PDFJS.getDocument(url).then(function (pdfDoc_) {
pdfDoc = pdfDoc_;
document.getElementById('page_count').textContent = pdfDoc.numPages;
// Initial/first page rendering
renderPage(pageNum);
});
//The PdfRead object is a browser-aware reading device that the User will
//manipulate to read the page. Basically, a wrapper around the PdfView object.
var frame = document.getElementById('pdfcanvas');
var zoom_widget = document.getElementById('pdf-page-zoom');
// Keep track of certain values inside the most interesting nodes of the DOM
var state = {
get ctop () { return frame.lastChild.offsetTop },
get ftop () { return frame.scrollTop },
get fsh () { return frame.scrollHeight },
get fh () { return frame.offsetHeight },
};
// Decrease the Zoom, acting on the scale
this.zoomMinus = function (val) {
doc.page.scale -= (val) ? val : 0.25;
zoom_widget.innerText = doc.page.scale * 100;
};
// Increase the Zoom, acting on the scale
this.zoomPlus = function (val) {
doc.page.scale += (val) ? val : 0.25;
zoom_widget.innerText = doc.page.scale * 100;
};
// Controller: monitor for frame scroll events and advance page rendering
frame.onscroll = function () {
var test = (state.fsh - (state.fh + state.ftop));
if (test < 0 && doc.page.head < doc.page.last) {
doc.page.number++;
}
};
// Init the widgets
zoom_widget.innerText = doc.page.scale * 100;
</script>
我试图将两者整合在一起并向我的查看器添加缩放，但是没有成功。与pdf.js的复杂性相比，我的JavaScript知识非常有限，但是我想知道是否有人可以帮助我解决我的问题。任何建议，方向，代码将不胜感激。
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Simple PDF.js with zoom</title>
<script src="pdfjs/build/pdf.js"></script>
</head>
<body>
<h1>Simple PDF.js with zoom</h1>
<button id="nextbutton" type="button">next page</button>
<button id="prevbutton" type="button">prev page</button>
<button id="zoominbutton" type="button">zoom in</button>
<button id="zoomoutbutton" type="button">zoom out</button>
<br>
<canvas id="the-canvas" style="border:1px solid black"></canvas>
<script id="script">
var pageNum = 1;
var pdfScale = 1; // make pdfScale a global variable
var shownPdf; // another global we'll use for the buttons
var url = './helloworld.pdf' // PDF to load: change this to a file that exists;
function renderPage(page) {
var scale = pdfScale; // render with global pdfScale variable
var viewport = page.getViewport(scale);
var canvas = document.getElementById('the-canvas');
var context = canvas.getContext('2d');
canvas.height = viewport.height;
canvas.width = viewport.width;
var renderContext = {
canvasContext: context,
viewport: viewport
};
page.render(renderContext);
}
function displayPage(pdf, num) {
pdf.getPage(num).then(function getPage(page) { renderPage(page); });
}
var pdfDoc = PDFJS.getDocument(url).then(function getPdfHelloWorld(pdf) {
displayPage(pdf, 1);
shownPdf = pdf;
});
var nextbutton = document.getElementById("nextbutton");
nextbutton.onclick = function() {
if (pageNum >= shownPdf.numPages) {
return;
}
pageNum++;
displayPage(shownPdf, pageNum);
}
var prevbutton = document.getElementById("prevbutton");
prevbutton.onclick = function() {
if (pageNum <= 1) {
return;
}
pageNum--;
displayPage(shownPdf, pageNum);
}
var zoominbutton = document.getElementById("zoominbutton");
zoominbutton.onclick = function() {
pdfScale = pdfScale + 0.25;
displayPage(shownPdf, pageNum);
}
var zoomoutbutton = document.getElementById("zoomoutbutton");
zoomoutbutton.onclick = function() {
if (pdfScale <= 0.25) {
return;
}
pdfScale = pdfScale - 0.25;
displayPage(shownPdf, pageNum);
}
</script>
</body>
</html>
很抱歉，我没有在上面检查您的代码以查看它与我的代码有何不同，或确定它不起作用，但这也许会满足您的需要。
我想添加放大和缩小...
@@ frabjous的答案很好，它提供的正是您所描述的内容。我也在修补它，现场演示：http://next.plnkr.co/edit/XQBGOhdzkX3zQ86Y
使用iframe并将URL作为参数传递似乎很简单！
/*
* Load pdf page to canvas and zoom it
*
* @url - url to pdf
* @pageNum - which page (start from 1)
* @width - canvas width
* @height - canvas height
* @zoom - zoom, 1=no zoom
* @posX - shift pdf on x axis (in pixels)
* @posY - shift pdf on y axis (in pixels)
*/
async function load(url,pageNum,width,height,zoom,posX,posY) {
let pdfjs = window['pdfjs-dist/build/pdf'];
pdfjs.GlobalWorkerOptions.workerSrc = '//mozilla.github.io/pdf.js/build/pdf.worker.js';
let pdf = await pdfjs.getDocument(url).promise;
let page = await pdf.getPage(pageNum);
let viewport = page.getViewport({scale:1});
let pY = viewport.transform[5]*zoom + posY;
viewport.transform=[zoom,0,0,-zoom,posX,pY];
let context = canvasPdf.getContext('2d');
canvasPdf.width = width;
canvasPdf.height = height;
let renderContext = {canvasContext: context, viewport};
var render = await page.render(renderContext).promise;
}
let url = "http://cors-anywhere.herokuapp.com/http://www.africau.edu/images/default/sample.pdf";
load(url,1,500,140,2,-140,-110);body {background: gray }<script src="//mozilla.github.io/pdf.js/build/pdf.js"></script>
<canvas id="canvasPdf"></canvas>