Pdf.js:使用 base64 文件源而不是 url 呈现 pdf 文件 [英] Pdf.js: rendering a pdf file using a base64 file source instead of url
问题描述
我正在尝试使用 pdf.js 从 pdf 呈现页面
I'm trying to render a page from a pdf with pdf.js
通常,使用 url,我可以这样做:
Normally, using a url, I can do this:
PDFJS.getDocument("http://www.server.com/file.pdf").then(function getPdfHelloWorld(pdf) {
//
// Fetch the first page
//
pdf.getPage(1).then(function getPageHelloWorld(page) {
var scale = 1.5;
var viewport = page.getViewport(scale);
//
// Prepare canvas using PDF page dimensions
//
var canvas = document.getElementById('the-canvas');
var context = canvas.getContext('2d');
canvas.height = viewport.height;
canvas.width = viewport.width;
//
// Render PDF page into canvas context
//
page.render({canvasContext: context, viewport: viewport});
});
});
但在这种情况下,我的文件是 base64 而不是网址:
But in this case, I have the file in base64 rather than an url:
data:application/pdf;base64,JVBERi0xLjUKJdDUxdgKNSAwIG9iaiA8PAovTGVuZ3RoIDE2NjUgICAgICAKL0ZpbHRlciAvRmxhdGVEZWNvZGUKPj4Kc3RyZWFtCnjarVhLc9s2...
如何做到这一点?
推荐答案
来自于源代码http://mozilla.github.com/pdf.js/build/pdf.js
/**
* This is the main entry point for loading a PDF and interacting with it.
* NOTE: If a URL is used to fetch the PDF data a standard XMLHttpRequest(XHR)
* is used, which means it must follow the same origin rules that any XHR does
* e.g. No cross domain requests without CORS.
*
* @param {string|TypedAray|object} source Can be an url to where a PDF is
* located, a typed array (Uint8Array) already populated with data or
* and parameter object with the following possible fields:
* - url - The URL of the PDF.
* - data - A typed array with PDF data.
* - httpHeaders - Basic authentication headers.
* - password - For decrypting password-protected PDFs.
*
* @return {Promise} A promise that is resolved with {PDFDocumentProxy} object.
*/
因此使用标准的 XMLHttpRequest(XHR) 来检索文档.问题在于 XMLHttpRequests 不支持 data: uris(例如 data:application/pdf;base64,JVBERi0xLjUK...).
So a standard XMLHttpRequest(XHR) is used for retrieving the document. The Problem with this is that XMLHttpRequests do not support data: uris (eg. data:application/pdf;base64,JVBERi0xLjUK...).
但是有可能将类型化的 Javascript 数组传递给函数.您唯一需要做的就是将 base64 字符串转换为 Uint8Array.您可以使用位于 https://gist.github.com/1032746
But there is the possibility of passing a typed Javascript Array to the function. The only thing you need to do is to convert the base64 string to a Uint8Array. You can use this function found at https://gist.github.com/1032746
var BASE64_MARKER = ';base64,';
function convertDataURIToBinary(dataURI) {
var base64Index = dataURI.indexOf(BASE64_MARKER) + BASE64_MARKER.length;
var base64 = dataURI.substring(base64Index);
var raw = window.atob(base64);
var rawLength = raw.length;
var array = new Uint8Array(new ArrayBuffer(rawLength));
for(var i = 0; i < rawLength; i++) {
array[i] = raw.charCodeAt(i);
}
return array;
}
tl;dr
var pdfAsDataUri = "data:application/pdf;base64,JVBERi0xLjUK..."; // shortened
var pdfAsArray = convertDataURIToBinary(pdfAsDataUri);
PDFJS.getDocument(pdfAsArray)
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