v0.4.0 - use Web Worker to generate PDF faster

package.json

@@ -1,6 +1,6 @@
 {
   "name": "musescore-downloader",
-  "version": "0.3.4",
+  "version": "0.4.0",
   "description": "download sheet music from musescore.com for free, no login or Musescore Pro required | 免登录、免 Musescore Pro，免费下载 musescore.com 上的曲谱",
   "main": "dist/main.js",
   "repository": {
@@ -18,6 +18,7 @@
   },
   "devDependencies": {
     "@rollup/plugin-json": "^4.0.0",
+    "@types/file-saver": "^2.0.1",
     "@types/pdfkit": "^0.10.4",
     "rollup": "^1.26.3",
     "rollup-plugin-commonjs": "^10.1.0",

src/main.ts

@@ -3,17 +3,19 @@ import "./meta"
 import { ScorePlayerData } from "./types"
 import { waitForDocumentLoaded } from "./utils"
 
-import PDFDocument from "pdfkit/lib/document"
-import saveAs from "file-saver/dist/FileSaver.js"
+import { PDFWorkerHelper } from "./worker-helper"
+import FileSaver from "file-saver/dist/FileSaver.js"
+
+const saveAs: typeof import("file-saver").saveAs = FileSaver.saveAs
 
 let pdfBlob: Blob
 
-const svgToPng = async (svgURL: string) => {
+const imgToBlob = async (imgURL: string) => {
     const imageElement = document.createElement("img")
     imageElement.style.display = "none"
     document.body.appendChild(imageElement)
 
-    imageElement.src = svgURL
+    imageElement.src = imgURL
 
     // wait until image loaded
     await new Promise((resolve) => {
@@ -34,7 +36,7 @@ const svgToPng = async (svgURL: string) => {
     canvasContext.clearRect(0, 0, width, height)
     canvasContext.drawImage(imageElement, 0, 0)
 
-    const data = canvas.toDataURL("image/png")
+    const data: Blob = await new Promise(resolve => canvas.toBlob(resolve, "image/png"))
 
     canvas.remove()
     imageElement.remove()
@@ -50,32 +52,15 @@ const generatePDF = async (svgURLs: string[], name?: string) => {
     const cachedImg = document.querySelector("img[id^=score_]") as HTMLImageElement
     const { naturalWidth: width, naturalHeight: height } = cachedImg
 
-    const imgDataList = await Promise.all(svgURLs.map(svgToPng))
+    const imgDataBlobList = await Promise.all(svgURLs.map(imgToBlob))
 
-    // @ts-ignore
-    const pdf = new (PDFDocument as typeof import("pdfkit"))({
-        // compress: true,
-        size: [width, height],
-        autoFirstPage: false,
-        margin: 0,
-        layout: "portrait",
-    })
+    const worker = new PDFWorkerHelper()
+    const pdfArrayBuffer = await worker.generatePDF(imgDataBlobList, width, height)
+    worker.terminate()
 
-    imgDataList.forEach((data) => {
-        pdf.addPage()
-        pdf.image(data, {
-            width,
-            height,
-        })
-    })
+    pdfBlob = new Blob([pdfArrayBuffer])
 
-    // TODO: webworker
-
-    // @ts-ignore
-    return pdf.getBlob().then((blob: Blob) => {
-        pdfBlob = blob
-        saveAs(blob, `${name}.pdf`)
-    })
+    saveAs(pdfBlob, `${name}.pdf`)
 }
 
 const getPagesNumber = (scorePlayerData: ScorePlayerData) => {
@@ -86,6 +71,17 @@ const getPagesNumber = (scorePlayerData: ScorePlayerData) => {
     }
 }
 
+const getImgType = (): "svg" | "png" => {
+    try {
+        const imgE: HTMLImageElement = document.querySelector("img[id^=score_]")
+        const { pathname } = new URL(imgE.src)
+        const imgtype = pathname.match(/\.(\w+)$/)[1]
+        return imgtype as "svg" | "png"
+    } catch (_) {
+        return null
+    }
+}
+
 const getTitle = (scorePlayerData: ScorePlayerData) => {
     try {
         return scorePlayerData.json.metadata.title
@@ -95,7 +91,7 @@ const getTitle = (scorePlayerData: ScorePlayerData) => {
 }
 
 const getScoreFileName = (scorePlayerData: ScorePlayerData) => {
-    return getTitle(scorePlayerData).replace(/\W+/g, "_")
+    return getTitle(scorePlayerData).replace(/[\s<>:"/\\|?*~\0\cA-\cZ]+/g, "_")
 }
 
 const main = () => {
@@ -121,8 +117,10 @@ const main = () => {
     const downloadBtn = btnsDiv.querySelector("button, .button") as HTMLElement
     downloadBtn.onclick = null
 
+    const imgType = getImgType() || "svg"
+
     const svgURLs = Array.from({ length: getPagesNumber(scorePlayer) }).fill(null).map((_, i) => {
-        return baseURL + `score_${i}.svg`
+        return baseURL + `score_${i}.${imgType}`
     })
 
     const downloadURLs = {
@@ -143,8 +141,7 @@ const main = () => {
         }
 
         const textNode = [...btn.childNodes].find((x) => {
-            return x.nodeName.toLowerCase() == "#text"
-                && x.textContent.includes("Download")
+            return x.textContent.includes("Download")
         })
         textNode.textContent = `Download ${name}`
 

src/worker-helper.ts

@@ -0,0 +1,29 @@
+
+import { PDFWorkerMessage } from "./worker"
+import { PDFWorker } from "../dist/cache/worker"
+
+const scriptUrlFromFunction = (fn: Function) => {
+    const blob = new Blob(["(" + fn.toString() + ")()"], { type: "application/javascript" })
+    return URL.createObjectURL(blob)
+}
+
+export class PDFWorkerHelper extends Worker {
+    constructor() {
+        const url = scriptUrlFromFunction(PDFWorker)
+        super(url)
+    }
+
+    generatePDF(imgDataBlobList: Blob[], width: number, height: number): Promise<ArrayBuffer> {
+        const msg: PDFWorkerMessage = [
+            imgDataBlobList,
+            width,
+            height,
+        ]
+        this.postMessage(msg)
+        return new Promise((resolve) => {
+            this.addEventListener("message", (e) => {
+                resolve(e.data)
+            })
+        })
+    }
+}

src/worker.ts

@@ -0,0 +1,61 @@
+
+/// <reference lib="webworker" />
+
+import PDFDocument from "pdfkit/lib/document"
+
+const generatePDF = async (imgDataUrlList: string[], width: number, height: number): Promise<ArrayBuffer> => {
+
+    // @ts-ignore
+    const pdf = new (PDFDocument as typeof import("pdfkit"))({
+        // compress: true,
+        size: [width, height],
+        autoFirstPage: false,
+        margin: 0,
+        layout: "portrait",
+    })
+
+    imgDataUrlList.forEach((data) => {
+        pdf.addPage()
+        pdf.image(data, {
+            width,
+            height,
+        })
+    })
+
+    // @ts-ignore
+    const buf: Uint8Array = await pdf.getBuffer()
+
+    return buf.buffer
+}
+
+const getDataURL = (blob: Blob): Promise<string> => {
+    return new Promise((resolve, reject) => {
+        const reader = new FileReader()
+        reader.onload = () => {
+            const result = reader.result
+            resolve(result as string)
+        }
+        reader.onerror = reject
+        reader.readAsDataURL(blob)
+    })
+}
+
+export type PDFWorkerMessage = [Blob[], number, number];
+
+onmessage = async (e) => {
+    const [
+        imgDataBlobList,
+        width,
+        height,
+    ] = e.data as PDFWorkerMessage
+
+    const dataURLs = await Promise.all(imgDataBlobList.map(getDataURL))
+
+    const pdfBuf = await generatePDF(
+        dataURLs,
+        width,
+        height,
+    )
+
+    postMessage(pdfBuf, [pdfBuf])
+}