Deleting indirect objects

Here is an observation I made while using this library.

Suppose you are editing a pdf file and you want to delete an indirect object that is referenced from a dictionary.
The relevant portions of the file can look like this

1000 0 obj << /StreamKey 2000 0 R /OtherKey whatever>>
endobj

...

2000 0 obj << /Length 34141 >> stream
... stream contents ...
endstream
endobj

How do you delete this stream?

Maybe

doc:TPDFDocument;
dict:TPDFDictionary;
obj:TPDFObject;
ref:TPdfIndRef;

obj:=dict.FindValueByKeyName('StreamKey', true);
obj.Purge;

No, it produces an error during saving. Similarly, the following code will not work either.

obj:=dict.FindValueByKeyName('StreamKey', false);
if obj is TPDFIndRef then begin
ref:=TPDFIndRef(obj);
ref.Obj.Purge;
ref.Purge
end;

Looking closer, one can find procedure TPDFDocument.DeleteObj(ObjNum, GenNum) that does exactly what needed. But alas, it is not public.

Fortunately, there is a way around that does not require modifying the library source. The address of this procedure is assigned to a published property of PageTree field. The final code is

ref:=TPDFIndRef(obj);
doc.PageTree.OnDeleteObj(ref.ObjNum, ref.GenNum);
and
dict.PurgeKey('StreamKey');

It works, but it is not exactly trivial.

It probably won't work for them. It looks like COM and DLL wrappers only expose the top level interface, TiSedQuickPdf class, not the underlying classes, and pdf objects (Cos layer in Adobe terms) are pretty low level.