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<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Previous/Next example</title>
</head>
<body>
<h1>'Previous/Next' example</h1>
<div>
<button id="prev">Previous</button>
<button id="next">Next</button>
<span>Page: <span id="page_num"></span> / <span id="page_count"></span></span>
</div>
<div>
<canvas id="the-canvas" style="border: 1px solid black; direction: ltr;"></canvas>
</div>
<script src="../../node_modules/pdfjs-dist/build/pdf.js"></script>
<script id="script">
//
// If absolute URL from the remote server is provided, configure the CORS
// header on that server.
//
var url = '../../web/compressed.tracemonkey-pldi-09.pdf';
//
// 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.
//
pdfjsLib.GlobalWorkerOptions.workerSrc =
'../../node_modules/pdfjs-dist/build/pdf.worker.js';
var pdfDoc = null,
pageNum = 1,
pageRendering = false,
pageNumPending = null,
scale = 0.8,
canvas = document.getElementById('the-canvas'),
ctx = canvas.getContext('2d');
/**
* 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: scale, });
// Support HiDPI-screens.
var outputScale = window.devicePixelRatio || 1;
canvas.width = Math.floor(viewport.width * outputScale);
canvas.height = Math.floor(viewport.height * outputScale);
canvas.style.width = Math.floor(viewport.width) + "px";
canvas.style.height = Math.floor(viewport.height) + "px";
var transform = outputScale !== 1
? [outputScale, 0, 0, outputScale, 0, 0]
: null;
// Render PDF page into canvas context
var renderContext = {
canvasContext: ctx,
transform: transform,
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 = num;
}
/**
* If another page rendering in progress, waits until the rendering is
* finished. 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.
*/
var loadingTask = pdfjsLib.getDocument(url);
loadingTask.promise.then(function(pdfDoc_) {
pdfDoc = pdfDoc_;
document.getElementById('page_count').textContent = pdfDoc.numPages;
// Initial/first page rendering
renderPage(pageNum);
});
</script>
</body>
</html>
|
