Unimplemented Features in Xpdf

This list corresponds to Xpdf 4.00.02 and PDF 1.7.

Categories are as follows:

feature category PDF Ref (1.7)
Chapter 3: Syntax
F/FFilter/FDecodeParms keys (external file) in stream dictionaries appearance 3.2.7 (p.60)
encryption algorithm 3
(note: undocumented and illegal to reverse engineer)
appearance 3.5 (p.115)
revision 3 security bits misc 3.5.2 (p.121)
public-key security handlers appearance 3.5.3 (p.126)
crypt filters
(partially implemented)
appearance 3.5.4 (p.129),
3.3.9 (p.88),
3.5 (p.115)
PDF version as Version key in Catalog dictionary misc 3.6.1 (p.136)
PageLayout and PageMode keys in Catalog dictionary user interface 3.6.1 (p.137)
OpenAction key in Catalog dictionary user interface 3.6.1 (p.137)
user space units - UserUnit key in Page dictionary
(partially implemented)
optional appearance 3.6.2 (p.148)
Order key in interpolated function dictionaries optional appearance 3.9.1 (p.165)
embedded file streams misc 3.10.3 (p.179)
URLs as file specifications misc 3.10.4 (p.183)
Chapter 4: Graphics
use of BlackPoint in CalGray, CalRGB, and Lab color spaces color management 4.5.4 (p.236)
NChannel-subtype DeviceN color spaces optional appearance 4.5.5 (p.269)
DeviceN color space attributes
(partially implemented)
color management 4.5.5 (p.272)
color operators not allowed in Type 3 glyphs and uncolored tiling patterns error checking 4.5.7 (p.281)
'Interpolate' flag in image dictionaries
(partially implemented)
optional appearance 4.8.4 (p.333)
'SMaskInData' field for JPX images transparency 4.8.4 (p.334)
alternate images optional appearance 4.8.4 (p.339)
reference XObjects optional appearance 4.9.3 (p.353)
optional content auto state (usage and usage application dicts) optional appearance / user interface 4.10 (p.380)
Chapter 5: Text
text knockout transparency 5.2.7 (p.395)
Chapter 6: Rendering
black generation and undercolor removal (when converting DeviceRGB to DeviceCMYK) color management 6.2.3 (p.473)
halftones color management 6.4 (p.478)
smoothness tolerance optional appearance 6.5.2 (p.501)
Chapter 7: Transparency
blending color space (for transparency groups and page groups); blending in CalRGB, CalGray, ICCBased color spaces
(currently handled for soft masks, but not for transparency groups)
transparency 7.5.2 (p.538), 7.5.4 (p.543), 7.5.5 (p.547), 7.6.1 (p.551)
shape vs. opacity; the "alpha is shape" (AIS) flag transparency 7.5.3 (p.539)
transfer function for soft masks transparency 7.5.4 (p.543)
page groups (transparency group in page object) transparency 7.5.5 (p.546), 7.3.6 (p.532)
transparency in patterns transparency 7.5.6 (p.550)
rendering parameters and transparency transparency 7.6.4 (p.563)
Chapter 8: Interactive Features
viewer preferences user interface 8.1 (p.569)
zoom factor in destinations user interface 8.2.1 (p.573)
color and style flags for outline entries user interface 8.2.2 (p.577)
thumbnail images user interface 8.2.3 (p.579)
collections user interface 8.2.4 (p.588)
page labels user interface 8.3.1 (p.580)
article threads user interface 8.3.2 (p.582)
presentation features user interface 8.3.3 (p.584)
annotation types other than links, widgets, and stamps
(partially implemented)
user interface / appearance 8.4 (p.590)
trigger events / additional-actions dictionaries (in annotations, fields, pages, and catalog) user interface 8.5.2 (p.632)
action types other than GoTo, GoToR, Launch, URI, Named; this includes JavaScript actions user interface 8.5.3 (p.636)
interactive forms (AcroForms), FDF files user interface / appearance 8.6 (p.656)
XFA forms
(partially implemented)
user interface / appearance 8.6.7 (p.722)
digital signatures misc 8.7 (p.706)
measurement properties user interface 8.8 (p.725)
document requirements user interface 8.9 (p.751)
Chapter 9: Multimedia Features
multimedia features appearance 9 (p.733)
Chapter 10: Document Interchange
XML metadata streams misc 10.2.2 (p.845)
logical structure text extraction 10.6 (p.855)
tagged PDF misc 10.7 (p.883)
accessibility support text extraction / misc 10.8 (p.935)
Web Capture support misc 10.9 (p.946)
prepress support misc 10.10 (p.912)
Appendix F: Linearized PDF
make use of linearization hints
(note: this is covered by an Adobe patent)
misc F (p.961)