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import ApiManager, { Registration } from "./ApiManager";
import { Method } from "../RouteManager";
import RouteSubscriber from "../RouteSubscriber";
import { existsSync, createReadStream, createWriteStream } from "fs";
import * as Pdfjs from 'pdfjs-dist/legacy/build/pdf';
import { createCanvas } from "canvas";
const imageSize = require("probe-image-size");
import * as express from "express";
import * as path from "path";
import { Directory, serverPathToFile, clientPathToFile, pathToDirectory } from "./UploadManager";
import { red } from "colors";
import { resolve } from "path";
export default class PDFManager extends ApiManager {
protected initialize(register: Registration): void {
register({
method: Method.POST,
subscription: new RouteSubscriber("thumbnail"),
secureHandler: async ({ req, res }) => {
const { coreFilename, pageNum, subtree } = req.body;
return getOrCreateThumbnail(coreFilename, pageNum, res, subtree);
}
});
}
}
async function getOrCreateThumbnail(coreFilename: string, pageNum: number, res: express.Response, subtree?: string): Promise<void> {
const resolved = `${coreFilename}-${pageNum}.png`;
return new Promise<void>(async resolve => {
const path = serverPathToFile(Directory.pdf_thumbnails, resolved);
if (existsSync(path)) {
const existingThumbnail = createReadStream(path);
const { err, viewport } = await new Promise<any>(resolve => {
imageSize(existingThumbnail, (err: any, viewport: any) => resolve({ err, viewport }));
});
if (err) {
console.log(red(`In PDF thumbnail response, unable to determine dimensions of ${resolved}:`));
console.log(err);
return;
}
dispatchThumbnail(res, viewport, resolved);
} else {
await CreateThumbnail(coreFilename, pageNum, res, subtree);
}
resolve();
});
}
async function CreateThumbnail(coreFilename: string, pageNum: number, res: express.Response, subtree?: string) {
const part1 = subtree ?? "";
const filename = `${part1}${coreFilename}.pdf`;
const sourcePath = resolve(pathToDirectory(Directory.pdfs), filename);
const documentProxy = await Pdfjs.getDocument(sourcePath).promise;
const factory = new NodeCanvasFactory();
const page = await documentProxy.getPage(pageNum);
const viewport = page.getViewport({ scale: 1, rotation: 0, dontFlip: false });
const { canvas, context } = factory.create(viewport.width, viewport.height);
const renderContext = {
canvasContext: context,
canvasFactory: factory,
viewport
};
await page.render(renderContext).promise;
const pngStream = canvas.createPNGStream();
const resolved = `${coreFilename}-${pageNum}.png`;
const pngFile = serverPathToFile(Directory.pdf_thumbnails, resolved);
const out = createWriteStream(pngFile);
pngStream.pipe(out);
return new Promise<void>((resolve, reject) => {
out.on("finish", () => {
dispatchThumbnail(res, viewport, resolved);
resolve();
});
out.on("error", error => {
console.log(red(`In PDF thumbnail creation, encountered the following error when piping ${pngFile}:`));
console.log(error);
reject();
});
});
}
function dispatchThumbnail(res: express.Response, { width, height }: Pdfjs.PageViewport, thumbnailName: string) {
res.send({
path: clientPathToFile(Directory.pdf_thumbnails, thumbnailName),
width,
height
});
}
class NodeCanvasFactory {
create = (width: number, height: number) => {
const canvas = createCanvas(width, height);
const context = canvas.getContext('2d');
return {
canvas,
context
};
}
reset = (canvasAndContext: any, width: number, height: number) => {
canvasAndContext.canvas.width = width;
canvasAndContext.canvas.height = height;
}
destroy = (canvasAndContext: any) => {
canvasAndContext.canvas.width = 0;
canvasAndContext.canvas.height = 0;
canvasAndContext.canvas = null;
canvasAndContext.context = null;
}
}
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