If your Office files (Word/Excel/PowerPoint) are hosted in SharePoint / OneDrive for Business (Office 365) and you want to export them as images (PNG/JPG) programmatically, the most reliable approach is:

✅ Use Microsoft Graph → Convert to PDF → Convert PDF to Image

Because:

• Graph can convert Office docs to PDF reliably

• Then Node/NestJS can render PDF pages into PNG/JPG with good quality

1) Architecture Overview (Simple Flow)

SharePoint file (docx/xlsx/pptx)

→ Microsoft Graph: download as PDF

→ NestJS: convert PDF pages → PNG/JPG

→ Store in S3/local/public folder and return URLs

2) Prerequisites (One-time Setup)

✅ Azure App Registration

1. Azure Portal → App registrations → New

2. Create a Client Secret

3. Add Microsoft Graph permissions (Application):

• Sites.Read.All (or Files.Read.All)

4. Grant Admin Consent

You’ll need these environment variables:

AZURE_TENANT_ID=xxxxx
AZURE_CLIENT_ID=xxxxx
AZURE_CLIENT_SECRET=xxxxx

3) Get App Token in NestJS (Client Credentials)

import { ConfidentialClientApplication } from "@azure/msal-node";

export class GraphAuthService {
  private cca = new ConfidentialClientApplication({
    auth: {
      clientId: process.env.AZURE_CLIENT_ID!,
      authority: `https://login.microsoftonline.com/${process.env.AZURE_TENANT_ID!}`,
      clientSecret: process.env.AZURE_CLIENT_SECRET!,
    },
  });

  async getAppToken(): Promise<string> {
    const result = await this.cca.acquireTokenByClientCredential({
      scopes: ["https://graph.microsoft.com/.default"],
    });
    if (!result?.accessToken) throw new Error("No access token");
    return result.accessToken;
  }
}

4) Download SharePoint File as PDF via Graph

This is the key endpoint:

GET /drives/{driveId}/items/{itemId}/content?format=pdf

import axios from "axios";

export class GraphFileService {
  constructor(private auth: GraphAuthService) {}

  async downloadAsPdf(driveId: string, itemId: string): Promise<Buffer> {
    const token = await this.auth.getAppToken();

    const url = `https://graph.microsoft.com/v1.0/drives/${driveId}/items/${itemId}/content?format=pdf`;

    const res = await axios.get(url, {
      headers: { Authorization: `Bearer ${token}` },
      responseType: "arraybuffer",
      maxRedirects: 5,
    });

    return Buffer.from(res.data);
  }
}

✅ Works for Word / Excel / PowerPoint

⚠️ Large Excel sheets may become multi-page PDFs depending on print layout.

5) Convert PDF → PNG/JPG in Node/NestJS

There are many ways. One stable approach is using Poppler (pdftocairo) on Linux servers.

Install (Ubuntu)

sudo apt-get update
sudo apt-get install -y poppler-utils

Convert PDF buffer to images (example)

You can write the PDF to a temp file, then run pdftocairo.

import { promises as fs } from "fs";
import path from "path";
import { execFile } from "child_process";
import { promisify } from "util";

const execFileAsync = promisify(execFile);

export class PdfToImageService {
  async pdfToPngPages(pdfBuffer: Buffer, outDir: string) {
    await fs.mkdir(outDir, { recursive: true });

    const pdfPath = path.join(outDir, "source.pdf");
    await fs.writeFile(pdfPath, pdfBuffer);

    // outputs: page-1.png, page-2.png ...
    await execFileAsync("pdftocairo", [
      "-png",
      "-r",
      "200",
      pdfPath,
      path.join(outDir, "page"),
    ]);

    // Return file list
    const files = await fs.readdir(outDir);
    return files.filter((f) => f.startsWith("page") && f.endsWith(".png"));
  }
}

You can then:

• upload generated images to S3

• or serve them from /public

6) Quick Alternative: Graph Thumbnails (Preview Images)

If you just want a quick preview image (not full quality):

GET /drives/{driveId}/items/{itemId}/thumbnails

Graph returns small/medium/large image URLs (if supported).

Final Notes:

✅ SharePoint এর Office file কে programmatically image বানাতে চাইলে—

সবচেয়ে safe method:

Graph → PDF → Image

কারণ Word/Excel/PPT সরাসরি image export সবসময় consistent না, কিন্তু PDF conversion বেশ reliable.

Ref: https://learn.microsoft.com/en-us/graph/api/driveitem-list-thumbnails?view=graph-rest-1.0&utm_source=chatgpt.com&tabs=http

https://learn.microsoft.com/en-us/graph/api/driveitem-get-content-format?view=graph-rest-1.0&utm_source=chatgpt.com&tabs=http