Class PdfJsDocument

src/scripts/contentCapture/pdfJsDocument.ts:8–106

import * as _ from "lodash";

export class PdfJsDocument implements PdfDocument {
	private pdf: PDFDocumentProxy;

	constructor(pdf: PDFDocumentProxy) {
		this.pdf = pdf;
	}

	public numPages(): number {
		return this.pdf.numPages;
	}

	public getByteLength(): Promise<number> {
		return this.getData().then((buffer) => {
			return Promise.resolve(buffer.length);
		});
	}

	public getData(): Promise<Uint8Array> {
		return new Promise<Uint8Array>((resolve) => {
			this.pdf.getData().then((buffer) => {
				resolve(buffer);
			});
		});
	}

	public getPageListAsDataUrls(pageIndexes: number[]): Promise<string[]> {
		let dataUrls: string[] = new Array(pageIndexes.length);
		return new Promise((resolve) => {
			for (let i = 0; i < pageIndexes.length; i++) {
				this.getPageAsDataUrl(pageIndexes[i]).then((dataUrl) => {
					dataUrls[i] = dataUrl;
					if (ArrayUtils.isArrayComplete(dataUrls)) {
						resolve(dataUrls);
					}
				});
			}
		});
	}

	public getPageAsDataUrl(pageIndex: number): Promise<string> {
		return new Promise<string>((resolve) => {
			// In pdf.js, indexes start at 1
			this.pdf.getPage(pageIndex + 1).then((page) => {
				// Issue #369: When the scale is set to 1, we end up with poor quality images
				// on high resolution machines. The best explanation I found for this was in
				// this article: http://stackoverflow.com/questions/35400722/pdf-image-quality-is-bad-using-pdf-js
				// Note that we played around with setting the scale from 3-5, which looked better on high
				// resolution monitors - but did not look good at all at lower resolutions. scale=2 seems
				// to be the happy medium.
				let viewport = page.getViewport(2 /* scale */);
				let canvas = document.createElement("canvas") as HTMLCanvasElement;
				let context = canvas.getContext("2d");
				canvas.height = viewport.height;
				canvas.width = viewport.width;

				let renderContext = {
					canvasContext: context,
					viewport: viewport