Separating Transparent Layers
through
Layer Information Exchange
Bernard Sarel and
Michal Irani
ECCV'2004.
Abstract
In this paper we present an approach for separating two transparent
layers in images and video sequences. Given two initial unknown physical
mixtures, I1 and I2, of real scene layers, L1
and L2, we seek a layer separation which minimizes the structural
correlations across the two layers, at every image point. Such a
separation is achieved by transferring local grayscale structure from one image
to the other wherever it is highly correlated with the underlying local
grayscale structure in the other image, and vice versa. This bi-directional
transfer operation, which we call the “layer information exchange”,
is performed on diminishing window sizes, from global image windows (i.e., the
entire image), down to local image windows, thus detecting similar grayscale
structures at varying scales across pixels. We show the applicability of this
approach to various real-world scenarios, including image and video
transparency separation. In particular, we show that this approach can be used
for separating transparent layers in images obtained under different
polarizations, as well as for separating complex non-rigid transparent
motions in video sequences. These can be done without prior knowledge of the
layer mixing model (simple additive, alpha-mated composition with an unknown
alpha-map, or other), and under unknown complex temporal changes (e.g., unknown
varying lighting conditions).
Paper
in pdf
Some example results:
We show here some video sequence results. For image results,
please look in the paper.
Example 1:
Synthetically Mixed Sequence
In this example we have synthetically additively mixed two video sequences into one, to serve as the input for the “Layer Information Exchange” algorithm. The first video sequence has a static image of a woman that translates in the field of view. We have artificially added periodic illumination changes to this sequence (dimming and brightening). The second video sequence portrays the non-rigid motions of small water fountain.
The following MPEG file shows the input sequence and the two recovered video sequence layers. Note that the illumination changes are clearly recovered in the woman video sequence.
Example 2:
Real Video Transparency
In this example we show a real video transparency sequence. The scene was taken at the entrance to one of the buildings here at the Weizmann Institute of Science (see sketch below).
A camera was placed pointing at a swinging entrance door to a building. The view of the camera includes the scene reflected from the swinging door (the panorama behind the camera), and the scene perceived through the swinging door (the building’s entrance hall). A man is walking behind the camera, thus his image is reflected from the door (along with the back panorama), while a statue and some greenery is seen through the door (in the entrance hall). The indoors scene is static, while the reflected outdoor scene has objects with non-rigid motion (the man), and changing illumination (due to the AGC function of the camera).
Statue Sequence - Input (810K avi) |
|
|
The original filmed input video sequence |
The first recovered layer Portrays the walking man and
the back panorama reflected in the swinging door. |
The second recovered layer Portrays the indoor scene with the statue and greenery |