Attach (recommended) or Link to PDF file here:

Configuration:
- Web browser and its version: Chrome 91.0.4472.124
- Operating system and its version: Win 10
- PDF.js version: 2.8.335
- Is a browser extension: Nope.

I'm trying to list and extract data form each element of a form created in a PDF file.
I have some image elements detected as Btn (button) and without any indice about the image.

`const items = await pdfPage.getAnnotations();

for (const item of items) {

    // With 'TestImage' as the name of one on my image elements
    if (item.fieldName === 'TestImage') {
        console.log('TestImage', item);
    }
}`

Gives:

TestImage 
{annotationFlags: 4, borderStyle: {…}, color: Uint8ClampedArray(3), contents: "", hasAppearance: true, …}
actions: {Action: Array(1)}
alternativeText: ""
annotationFlags: 4
annotationType: 20
borderStyle:
    dashArray: [3]
    horizontalCornerRadius: 0
    style: 1
    verticalCornerRadius: 0
    width: 0
checkBox: false
color: 
Uint8ClampedArray(3) 
[0, 0, 0]
contents: ""
defaultAppearanceData:
    fontColor: Uint8ClampedArray(3) [0, 0, 0]
    fontName: "HeBo"
    fontSize: 12
defaultFieldValue: null
fieldFlags: 65536
**fieldName: "TestImage"**
**fieldType: "Btn"**
fieldValue: null
hasAppearance: true
hidden: false
id: "57R"
isTooltipOnly: false
modificationDate: null
pushButton: true
radioButton: false
readOnly: false
rect: (4) [383.563, 623.486, 527.808, 744.176]
subtype: "Widget"

Any idea?

In front of that, I'm able to get images from regular image fields (out of Forms) without any context (the  location and the size used in the PDF):


```
// Potential image types
const imagesObjectsTypes = [
    pdfjsLib.OPS.paintImageMaskXObject,
    pdfjsLib.OPS.paintImageMaskXObjectGroup,
    pdfjsLib.OPS.paintImageXObject, // <- 85
    pdfjsLib.OPS.paintInlineImageXObject,
    pdfjsLib.OPS.paintInlineImageXObjectGroup,
    pdfjsLib.OPS.paintImageXObjectRepeat,
    pdfjsLib.OPS.paintImageMaskXObjectRepeat,   
];

const operatorsList = await pdfPage.getOperatorList();

for (let i = 0; i < operatorsList.fnArray.length; i++) {

    const type = operatorsList.fnArray[i];

    if (imagesObjectsTypes.indexOf(type) >= 0) {

        const image = pdfPage.objs.get(operatorsList.argsArray[i][0]);

        console.log('Image detected:')
        console.log(image);
        console.log(operatorsList.argsArray[i]);
    }
}

```
Gives

Image detected:
width: 1067,
height: 600,
kind: 2, data: Uint8ClampedArray(1920600)} data: Uint8ClampedArray(1920600) [ …],
height: 600,
kind: 2,
width: 1067,

0: "img_p0_3"
1: 1067
2: 600

Thank you :)





expect(data.length).toEqual(2
      const [oldData, newData] = data;
      expect(oldData.ref).toEqual(Ref.get(123, 0)
      expect(newData.ref).toEqual(Ref.get(1, 0)
      oldData.data = oldData.data.replace(/\(D:[0-9]+\)/, "(date)"
      expect(oldData.data).toEqual(
        "123 0 obj\n" +
          "<< /Type /Annot /Subtype /Widget /FT /Ch /DA (/Helv 5 Tf) /DR " +
          "<< /Font << /Helv 314 0 R>>>> " +
          "/Rect [0 0 32 10] /Opt [(A) (B) (C)] /V (C) " +
          "/AP << /N 1 0 R>> /M (date)>>\nendobj\n"
      
      expect(newData.data).toEqual(
        "1 0 obj\n" +
          "<< /Length 67 /Subtype /Form /Resources << /Font << /Helv 314 0 R>>>> " +
          "/BBox [0 0 32 10]>> stream\n" +
          "/Tx BMC q BT /Helv 5 Tf 1 0 0 1 0 0 Tm 2.00 2.00 Td (C) Tj ET Q EMC\n" +
          "endstream\nendobj\n"
      
    }
  }
  describe("LineAnnotation", function () {
    it("should set the line coordinates", async function () {
      const lineDict = new Dict(
      lineDict.set("Type", Name.get("Annot")
      lineDict.set("Subtype", Name.get("Line")
      lineDict.set("L", [1, 2, 3, 4]
      const lineRef = Ref.get(122, 0
      const xref = new XRefMock([{ ref: lineRef, data: lineDict }]
      const { data } = await AnnotationFactory.create(