How to know if PDF.JS has finished rendering?

Question

I am using PDF.JS to render pdf pages into different canvas elements. my requirement is to capture the output of the canvas and to display it as an image. Is there some even

Answer 1

If you want to render all pages of pdf document in different canvases, all one by one synchronously this is kind of solution:

index.html

main.css

canvas {
    display: block;
}

main.js

$(function() {  
    var filePath = "document.pdf";

    function Num(num) {
        var num = num;

        return function () {
            return num;
        }
    };

    function renderPDF(url, canvasContainer, options) {
        var options = options || {
                scale: 1.5
            },          
            func,
            pdfDoc,
            def = $.Deferred(),
            promise = $.Deferred().resolve().promise(),         
            width, 
            height,
            makeRunner = function(func, args) {
                return function() {
                    return func.call(null, args);
                };
            };

        function renderPage(num) {          
            var def = $.Deferred(),
                currPageNum = new Num(num);
            pdfDoc.getPage(currPageNum()).then(function(page) {
                var viewport = page.getViewport(options.scale);
                var canvas = document.createElement('canvas');
                var ctx = canvas.getContext('2d');
                var renderContext = {
                    canvasContext: ctx,
                    viewport: viewport
                };

                if(currPageNum() === 1) {                   
                    height = viewport.height;
                    width = viewport.width;
                }

                canvas.height = height;
                canvas.width = width;

                canvasContainer.appendChild(canvas);

                page.render(renderContext).then(function() {                                        
                    def.resolve();
                });
            })

            return def.promise();
        }

        function renderPages(data) {
            pdfDoc = data;

            var pagesCount = pdfDoc.numPages;
            for (var i = 1; i <= pagesCount; i++) { 
                func = renderPage;
                promise = promise.then(makeRunner(func, i));
            }
        }

        PDFJS.disableWorker = true;
        PDFJS.getDocument(url).then(renderPages);       
    };

    var body = document.getElementById("body");
    renderPDF(filePath, body);
});