Pdf.js:使用base64文件源而不是url来呈现Pdf文件

Pdf.js: rendering a pdf file using a base64 file source instead of url

本文关键字：文件 Pdf url js 使用 base64      更新时间：2023-09-26

我正试图用pdf.js 从pdf中呈现一个页面

通常，使用url，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});
  });
});

但在这种情况下，我的文件是base64，而不是url:

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

如何做到这一点？

来自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。问题是XMLHttpRequest不支持data:uris（例如data:application/pdf；base64，JVBERi0xLjUK…）

但是也有可能将一个类型化的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

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)

根据示例，base64编码是直接支持的，尽管我自己还没有测试过。拿你的base64字符串（从文件中派生或用任何其他方法、POST/GET、websockets等加载），用atob将其转换为二进制文件，然后在PDFJS API上解析为getDocument，如PDFJS.getDocument({data: base64PdfData}); Codetoffel答案对我来说很好。

使用Accepted Answer检查IE并将dataURI转换为UInt8Array；PDFJS接受的表格

        Ext.isIE ? pdfAsDataUri = me.convertDataURIToBinary(pdfAsDataUri): '';
        convertDataURIToBinary: function(dataURI) {
          var BASE64_MARKER = ';base64,',
            base64Index = dataURI.indexOf(BASE64_MARKER) + BASE64_MARKER.length,
            base64 = dataURI.substring(base64Index),
            raw = window.atob(base64),
            rawLength = raw.length,
            array = new Uint8Array(new ArrayBuffer(rawLength));
          for (var i = 0; i < rawLength; i++) {
            array[i] = raw.charCodeAt(i);
          }
          return array;
        },

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