Convert pdf to image before uploading it to s3

Question

I have a current setup in React js where I upload files to s3 using multipart upload as buffer.However if the file format is pdf,video,audio etc. I want to convert it to image before uploading to s3; think of it as thumbnail generation.I have read a lot about this but could not find a right solution for my needs, can please someone suggest some possible solution?(where backend is not involved at all) PS:I have looked at pdf.js but dont know how to use it while my file type is buffer and what type will it return and can I upload it the same way to S3.A small example would help miles. Thanks in advance !!

    var pdfData = buffer;
    var pdfjsLib = window['pdfjs-dist/build/pdf'];

    pdfjsLib.GlobalWorkerOptions.workerSrc = 'https://cdnjs.cloudflare.com/ajax/libs/pdf.js/2.0.943/pdf.worker.min.js';

    var loadingTask = pdfjsLib.getDocument({data: pdfData});
    loadingTask.promise.then(function(pdf) {
        console.log('PDF loaded');
        pdf.getPage(1).then(function getPageHelloWorld(page) {

            var scale = 1.5;
            var viewport = page.getViewport(scale);
            console.log('page',viewport);
            //
            // Prepare canvas using PDF page dimensions
            //
            var canvas = document.getElementById('bulk-thumbnails');
            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});
        });

Answer 1

According to the 2nd example of pdf.js (in the link below) you can also load pdf file using its base64 code.

https://mozilla.github.io/pdf.js/examples/index.html#interactive-examples

var pdfData = atob('PDF file in Base64...');
var pdfjsLib = window['pdfjs-dist/build/pdf'];

// The workerSrc property shall be specified.
pdfjsLib.GlobalWorkerOptions.workerSrc = '//mozilla.github.io/pdf.js/build/pdf.worker.js';

// Using DocumentInitParameters object to load binary data.
var loadingTask = pdfjsLib.getDocument({data: pdfData});
loadingTask.promise.then(function(pdf) {
  console.log('PDF loaded');
});

And To load pdf file as base64 code you can actually use HTML5 FileReader like this

function getBase64(file) {
   var reader = new FileReader();
   reader.readAsDataURL(file);
   reader.onload = function () {
     console.log(reader.result);
   };
   reader.onerror = function (error) {
     console.log('Error: ', error);
   };
}

var file = document.querySelector('#files > input[type="file"]').files[0];
getBase64(file); // prints the base64 string

Referenced from How to convert file to base64 in JavaScript?

Hope it helps

Answer 2

I have built a functionality on the above link check this out

StackBlitz