If you change a picture with a filter, e.g. using the Sharpen tool, then these
changes cannot be undone once you've saved a document and re-opened it, or after
the undo cache has been cleared (e.g. after updating a table of contents). OO
saves the changed picture in the .odt file -- even if the picture was linked.

This means that:

* If you link a picture and then later change the original picture, when you
re-open the document, OO will not reload the new picture.

* Likewise, even if you link a picture, OO saves the picture in the .odt file,
so the .odt file is made larger.

* You cannot see what effects you've applied to a picture.

* To undo any changes to a picture, you need to delete the picture from the
document and reload it.

Please also refer to
http://user.services.openoffice.org/en/forum/viewtopic.php?f=7&t=15240

Tested on OpenOffice Writer 3.0.1 on both Windows Vista and Ubuntu Hardy.

To reproduce, first example:
----------------------------

1. Insert -> Picture -> From File... -> (choose a picture, e.g. a JPEG) -> Link
(tick the box)

2. Make filter changes to the picture, e.g. from the Picture toolbar, choose
Filter -> Sharpen.

At this point, you can undo. However...

3. Save.

4. Close the document.

If you open the document as a ZIP file, you'll notice that the changed picture
is saved, i.e. not the original picture.

5. Open the document.

There is no way to tell what filter tools you've used, nor can you undo the filters.

6. Close the document.

7. Change the original picture.

8. Open the document.

You'll notice that OO has not reloaded the new picture, but still shows the old
picture.

To reproduce, second example:
-----------------------------

Identical to the first example, except do not link, as follows:

1. Insert -> Picture -> From File... -> (choose a picture) -> Link (do *not*
tick the box)

Steps 2-5 are the same as for the first example.

Steps 6-8 are not relevant.

What would be more useful:
--------------------------

It would be more useful to store the original picture (if not linked) or to
never store the picture (if linked) in the .odt file, and instead store what
needs to be done to the picture.

I realise that this would mean a little extra CPU time every time the document
was opened, but with today's computers, it's no more than a fraction of a second.

At a minimum, allow the user to "reset" the picture to its default.

Preferably, also allow the user to see what filter tools have been applied
already and to change those tools (e.g. change the sharpen and soften tools to
show a number, e.g. positive for sharpen and negative for soften).

The original picture is always being worked on, so there will be no loss of
quality even if the user frequently changes his mind.

Advantages
----------

1. For a linked picture, OO will always load the latest version and apply the
chosen filters.

2. For a linked picture, OO will not store the picture, allowing the .odt file
to remain small.

3. The user will be able to undo or change any filters at any time.

4. The user will be able to see what changes have already been made.