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):

bold = "900";
      } else if (fontObj.bold) {
        bold = "bold";
      }
      const italic = fontObj.italic ? "italic" : "normal";
      const typeface = `"${name}", ${fontObj.fallbackName}`;
      
      
      
      
      let browserFontSize = size;
      if (size < MIN_FONT_SIZE) {
        browserFontSize = MIN_FONT_SIZE;
      } else if (size > MAX_FONT_SIZE) {
        browserFontSize = MAX_FONT_SIZE;
      }
      this.current.fontSizeScale = size / browserFontSize;
      this.ctx.font = `${italic} ${bold} ${browserFontSize}px ${typeface}`;
    }
    setTextRenderingMode(mode) {
      this.current.textRenderingMode = mode;
    }
    setTextRise(rise) {
      this.current.textRise = rise;
    }
    moveText(x, y) {
      this.current.x = this.current.lineX += x;
      this.current.y = this.current.lineY += y;
    }
    setLeadingMoveText(x, y) {