Hi Alex,

Background extraction IS indeed tricky.

First, different pictures require different tools. Everything where
the foreground color is essentially one color, such as drawings will
work best with a tool like Magic Wand. The foreground extraction Jenny
was improving is intended to be used on photographs and works best
when the fotograph features a clearly distinctive foreground but the
foreground can easily contain millions of colors and as of now, the
foreground can also have very fine structure. There is virtually no
tool that can deal with transparencies, reflections, and other nasty
stuff. When extracting objects with these issues you have to be lucky.

Second, the way to think of these semi-automatic extraction tools is
to compare them with a dish washer. Very often, the dish washer will
do a good job and clean your dishes. So it'll save you work and it'll
be cleaner than if you'd done it manually in the same time. However,
for some pieces, the dish washer just doesn't work. Often these are
the pieces that are particularly difficult, sometimes though you ask
yourself: Why is this glass still dirty -- it's like all the other
glasses? So there are people who do not want a dish washer because
they want to be in absolute control of the cleaning process. However,
would you stop producing, selling, using, and improving dish washers
in general, just because they don't work always? The answer is of
course: No because in sum they are useful.
Same with automatic foreground extraction methods: For some images
they save a lot of work, for others they might cause trouble. Some
people will never use the tools because they want to be in complete
control of the segmentation process. In sum they are useful though.


On Thu, Sep 17, 2009 at 10:57 PM, Alexandre Prokoudine
<alexandre.prokoud...@gmail.com> wrote:
> On Fri, Sep 18, 2009 at 2:34 AM, SorinN wrote:
>> Well, every background extraction is tricky - I tried PhotoshopCS 4
>> tools - they seems to be trivial to use and seem to be easy - but for
>> a complex task which need a lot of pixel precision you have to do a
>> lot of manually corrections too so the final feelig is a kind of
>> frustration - (with gimp magic wand progresive selection feature [drag
>> over layer left / right], I can do the same thing quicker).
> Are you talking about
> http://help.adobe.com/en_US/Photoshop/11.0/WSFD9BA8C5-31BA-4fec-81F3-CF04EE5295FCa.html
> ?
> Alexandre
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