Image XObject in PDF - Part 2

Question

Hi everyone,
With regard to the previous thread on "Image XObject in PDF", I posted a question on the retention of the image attribute saved on the PDF.
I understand from Irosenth that PDF only supports jpeg and "raw raster" images on storage. I also asked a question on libtiff and when does
Acrobat uses their own proprietiary tiff library. lrosenth highlighted that the library is only invoked when Acrobat saves and extracts images
from a PDF file and there is no other circumstances where the tiff library is used.
Question 1
How about PDF XFDF forms? I understand that in forms, we can specify a imagefield of contenttype:"Image/tif" with the base64 encoded
values of the tif image embedded in the form. In such case, will the tiff library be invoked by the Acrobat to parse and render the tif image?
Question 2
If the image libraries can be invoke in such a way, does this apply to other images such as JPEG. JPX, GIF and PNG?
Thanks

Answer 1

Hi Irosenth, thanks for the point.
However, I came across an xml-based form stored as a stream (flate-encoded)  in a PDF.
The decoded stream is as follows:
Isn't the self.tiff64 an base64-encoded form of a raw TIFF image (Not stored as an image XObject)?
<?xml version="1.0" encoding="UTF-8" ?>
<xdp:xdp xmlns:xdp="http://ns.adobe.com/xdp/">
<config xmlns="http://www.xfa.org/schema/xci/1.0/">
<present>
<pdf>
<version>1.65</version>
<interactive>1</interactive>
<linearized>1</linearized>
</pdf>
<xdp>
<packets>*</packets>
</xdp>
<destination>pdf</destination>
</present>
</config>
<template baseProfile="interactiveForms" xmlns="http://www.xfa.org/schema/xfa-template/2.4/">
<subform name="topmostSubform" layout="tb" locale="en_US">
<pageSet>
<pageArea id="PageArea1" name="PageArea1">
<contentArea name="ContentArea1" x="0pt" y="0pt" w="612pt" h="792pt" />
<medium short="612pt" long="792pt" stock="custom" />
</pageArea>
</pageSet>
<subform name="Page1" x="0pt" y="0pt" w="612pt" h="792pt">
<break before="pageArea" beforeTarget="#PageArea1" />
<bind match="none" />
<field name="ImageField1" w="28.575mm" h="1.39mm" x="37.883mm" y="29.25mm">
<ui>
<imageEdit />
</ui>
</field>
<?templateDesigner expand 1?>
</subform>
<?templateDesigner expand 1?>
</subform>
<?templateDesigner FormTargetVersion 24?>
<?templateDesigner Rulers horizontal:1, vertical:1, guidelines:1, crosshairs:0?>
<?templateDesigner Zoom 94?>
</template>
<xfa:datasets xmlns:xfa="http://www.xfa.org/schema/xfa-data/1.0/">
<xfa:data>
<topmostSubform>
<ImageField1 xfa:contentType="image/tif" href="">'''+self.tiff64 +'''</ImageField1>
</topmostSubform>
</xfa:data>
</xfa:datasets>
<PDFSecurity xmlns="http://ns.adobe.com/xtd/" print="1" printHighQuality="1" change="1" modifyAnnots="1" formFieldFilling="1" documentAssembly="1" contentCopy="1" accessibleContent="1" metadata="1" />
<form checksum="a5Mpguasoj4WsTUtgpdudlf4qd4=" xmlns="http://www.xfa.org/schema/xfa-form/2.8/">
<subform name="topmostSubform">
<instanceManager name="_Page1" />
<subform name="Page1">
<field name="ImageField1" />
</subform>
<pageSet>
<pageArea name="PageArea1" />
</pageSet>
</subform>
</form>
</xdp:xdp>