issue with snapshot capture and comparisons using gtk

["bharat tewari" <bharat tewari wipro com>]

hi guys
sorry if this topic is already brought out but currently i am trying to fix the issue in the image snapshot comparisons in the gnome-test-tool ( erstwhile gerd) and i have the following problem. Before that i will just explain how the gnome-test-tool works which will help. First we do a record session where in an application ( like nautilus, eog etc.) are started through this tool and the tool captures all the events that are generated during the recording time. Once you have done that, you can capture window snapshots using F5/F6 keys where in you can capture the window. The way it does is, it first creates a pixbuf and then copies the drawable ( i.e the window data) as gdk_pixbuf_get_from_drawable() passing colormap as NULL to this call.
After capturing the pixbuf, it writes it into a file by changing it to pixdata and then serializing the pixdata ( it also has support for png conversion but currently i am doing this to avoid any png related issues). Along with this, all the events are also captured into a file. This will end the record session.

While doing a playback, the event file is played back and this time again for the same window, the snapshot is again captured using the same mechanism as done during the record mode.

The snapshots are then compared to find out whether the record and the playback has generated the same output.

Now when i am trying to do the same for a nautilus/eog window which loads a png file ( any image file) and i do record and playback, most of the times the result is a pass where as when i try to do this comparison after resizing the nautilus/eog window which has a png loaded, it always fails. 
Can anybody point me as to what is being done wrongly here? We really need reliability in the tool and with these snapshots failing, we are unable to use this tool for test automations.
Since i am not subscribed to this list, please mail me your answers at bharat tewari wipro com