pdf.js：使用base64文件源而不是url渲染pdf文件

Question

我正在尝试使用pdf.js从pdf渲染页面

通常，使用网址，我可以这样做：

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});
  });
});

但是在这种情况下，我将文件放在base64中而不是url中：

data:application/pdf;base64,JVBERi0xLjUKJdDUxdgKNSAwIG9iaiA8PAovTGVuZ3RoIDE2NjUgICAgICAKL0ZpbHRlciAvRmxhdGVEZWNvZGUKPj4Kc3RyZWFtCnjarVhLc9s2...

如何做到这一点？

Answer 1

从http://mozilla.github.com/pdf.js/build/pdf.js的源代码中

/**
 * 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XMLHttpRequest（XHR）来检索文档。问题在于XMLHttpRequests不支持数据：uris（例如data：application/ pdf; base64，JVBERi0xLjUK …）。

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)