Attach (recommended) or Link to PDF file here:
[backgroundimage_not_visible_anonymisiert.pdf](https://github.com/mozilla/pdf.js/files/6544725/backgroundimage_not_visible_anonymisiert.pdf)


Configuration:
- Web browser and its version: Chrome Version 90.0.4430.212 (Offizieller Build) (x86_64)
- Operating system and its version: Windows 10, MacOs BigSur
- PDF.js version: 2.5.207
- Is a browser extension: no

Steps to reproduce the problem:
1. open the document in demo viewer.js
2.

What is the expected behavior? (add screenshot)
The backgroundimage gets rendered like in Acrobat Reader
<img width="1348" alt="Bildschirmfoto 2021-05-26 um 09 44 21" src="https://user-images.githubusercontent.com/1286150/119621970-00a82480-be07-11eb-8fed-f74ac04b840b.png">

What went wrong? (add screenshot)
Backgroundimage is not rendered only some  text
<img width="987" alt="Bildschirmfoto 2021-05-26 um 09 43 57" src="https://user-images.githubusercontent.com/1286150/119621938-fab24380-be06-11eb-92ac-4ecb2c9334b1.png">




Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

const POINT_TO_PROCESS_LIMIT = 1000;
  const POINT_TYPES = new Uint8Array([
    0, 2, 4, 0, 1, 0, 5, 4, 8, 10, 0, 8, 0, 2, 1, 0,
  ]);
  const width = imgData.width,
    height = imgData.height,
    width1 = width + 1;
  let i, ii, j, j0;
  const points = new Uint8Array(width1 * (height + 1));
  
  const lineSize = (width + 7) & ~7,
    data0 = imgData.data;
  const data = new Uint8Array(lineSize * height);
  let pos = 0;
  for (i = 0, ii = data0.length; i < ii; i++) {
    const elem = data0[i];
    let mask = 128;
    while (mask > 0) {
      data[pos++] = elem & mask ? 0 : 255;
      mask >>= 1;
    }
  }