Attach (recommended) or Link to PDF file here:
https://guichet.public.lu/dam-assets/catalogue-formulaires/tva/tva-option-aic-pers-morales/tva-option-aic-pers-morale-DE.pdf

Configuration:
- Web browser and its version: Firefox Nightly 91.0a1 (2021-06-26) (64-bit)
- Operating system and its version: Windows 10.0.19043.1052
- PDF.js version: N/A

Steps to reproduce the problem:
1. enableXFA in Firefox Nightly
2. Open form

What is the expected behavior? (add screenshot)
Header image is scaled properly
![image](https://user-images.githubusercontent.com/7104454/123525954-905d1f00-d6a2-11eb-840e-be30eee395e1.png)

What went wrong? (add screenshot)
Image is scaled to fit
![image](https://user-images.githubusercontent.com/7104454/123525957-96530000-d6a2-11eb-9991-bf7f37c6f1a5.png)


constructor(attributes) {
    super(TEMPLATE_NS_ID, "setProperty");
    this.connection = attributes.connection || "";
    this.ref = attributes.ref || "";
    this.target = attributes.target || "";
  }
}
class SignData extends XFAObject {
  constructor(attributes) {
    super(TEMPLATE_NS_ID, "signData",  true);
    this.id = attributes.id || "";
    this.operation = getStringOption(attributes.operation, [
      "sign",
      "clear",
      "verify",
    ]);
    this.ref = attributes.ref || "";
    this.target = attributes.target || "";
    this.use = attributes.use || "";
    this.usehref = attributes.usehref || "";
    this.filter = null;
    this.manifest = null;
  }
}
class Signature extends XFAObject {