Catching image from zbar when it recognised a bar code

[Tobias Mueller]

Hi.

I am using the zbar element and I would like to "catch" the image that
made zbar decode a barcode.
So I do not only want to get the decoded barcode, but also the image
which caused zbar to generate a signal.

The scenario is that an attacker could "inject", for a frame or two, a
malicious image. And I want to show the user "see, this image apparently
contained a barcode which decoded to this string".

My pipeline is this:
v4l2src ! tee name=t ! queue ! videoconvert ! zbar ! fakesink t. queue !
videoconvert ! xvimagesink

I tried to get my hands on the xvimagesink, i.e.
imagesink.get_last_sample().get_buffer().extract_dup(), but that data
doesn't seem to be anything useful for me.

Cheers,
  Tobi