PDF changes

- Scale pdf by 2, in order to read smaller QR Codes
- Read last page of PDF (2nd dose often on 2nd page)

src/process.js

@@ -1,22 +1,35 @@
-const PDFJS = require('pdfjs-dist')
-PDFJS.GlobalWorkerOptions.workerSrc = `https://cdnjs.cloudflare.com/ajax/libs/pdf.js/${PDFJS.version}/pdf.worker.js`
-
 import jpeg from 'jpeg-js'
-import { PNG } from 'pngjs'
+import {PNG} from 'pngjs'
+import * as PdfJS from 'pdfjs-dist'
 
+PdfJS.GlobalWorkerOptions.workerSrc = `https://cdnjs.cloudflare.com/ajax/libs/pdf.js/${PdfJS.version}/pdf.worker.js`
+
+// Processes a pdf file and returns it as ImageData
 export async function processPdf(file) {
-  var typedarray = new Uint8Array(file)
+    // Array to store ImageData information
+    const typedArray = new Uint8Array(file)
 
+    // PDF scale, increase to read smaller QR Codes
+    const pdfScale = 2;
+
+    // Get the canvas and context to render PDF
     const canvas = document.getElementById('canvas')
     const ctx = canvas.getContext('2d')
 
-  var loadingTask = PDFJS.getDocument(typedarray)
+    let loadingTask = PdfJS.getDocument(typedArray)
+
     await loadingTask.promise.then(async function (pdfDocument) {
-    const pdfPage = await pdfDocument.getPage(1)
-    const viewport = pdfPage.getViewport({ scale: 1 })
+        // Load last PDF page
+        const pageNumber = pdfDocument.numPages;
+
+        const pdfPage = await pdfDocument.getPage(pageNumber)
+        const viewport = pdfPage.getViewport({scale: pdfScale})
+
+        // Set correct canvas width / height
         canvas.width = viewport.width
         canvas.height = viewport.height
 
+        // render PDF
         const renderTask = pdfPage.render({
             canvasContext: ctx,
             viewport,
@@ -25,21 +38,22 @@ export async function processPdf(file) {
         return await renderTask.promise
     })
 
-  var imageData = ctx.getImageData(0, 0, canvas.width, canvas.height)
-
-  return imageData
+    // Return PDF Image Data
+    return ctx.getImageData(0, 0, canvas.width, canvas.height)
 }
 
+// Processes a JPEG File and returns it as ImageData
 export async function processJpeg(file) {
     return jpeg.decode(file)
 }
 
+// Processes a PNG File and returns it as ImageData
 export async function processPng(file) {
     return new Promise(async (resolve, reject) => {
-    let png = new PNG({ filterType: 4 })
+        let png = new PNG({filterType: 4})
 
         png.parse(file, (error, data) => {
-      if(error) {
+            if (error) {
                 reject()
             }