Patent Application
20120008852
1. Field of the Invention
The present invention generally relates to digital image processing, and more particularly to a system and method of enhancing depth of a three-dimensional (3D) image.
2. Description of Related Art
When three-dimensional (3D) objects are mapped onto a two-dimensional (2D) image plane by prospective projection, such as an image taken by a still camera or a video camera, a lot of information, particularly 3D depth information, disappears. A 3D imaging system, however, can convey 3D information to a viewer by recording 3D visual information or by re-creating the illusion of depth. Although the 3D imaging technique has been known for over a century, the 3D display becomes more practical and popular owing to availability of high-resolution and low-price displays such as liquid crystal displays (LCDs).
Conventional 3D imaging systems have some disadvantages such as limited depth range. Accordingly, the viewer oftentimes cannot distinguish objects that are supposed to possess distinct depth levels respectively.
For the reason that conventional 3D imaging systems could not effectively display 3D image or video, a need has arisen to propose a novel 3D imaging system and method with improved depth characteristics.
In view of the foregoing, it is an object of the embodiment of the present invention to provide a system and method of enhancing depth of a three-dimensional (3D) image to increase quality of a 3D image or video such that a viewer can perceive more depth levels.
According to one embodiment, a depth generator generates at least one depth map associated with an image. A depth enhancer enhances the depth map by stretching a depth histogram associated with the depth map, wherein the depth histogram is a distribution of depth levels of pixels of the image.
According to another embodiment, a depth map associated with an image is received, and the depth map is segmented into a number of divided depth maps. Subsequently, a number of local depth histograms are generated according to the divided depth maps respectively. Finally, the divided depth maps are individually enhanced by modifying depth characteristics of the image.
In step 31, a left (L) image 21A and a right (R) image 21B displayable in a 3D imaging system are received, followed by generating at least one depth map, in step 32, by a depth generator 22. For example, the depth generator 22 may generate a left depth map and a right depth map that correspond to the original left image and the right image respectively. In another example, the depth generator 22 may generate a single depth map. In the depth map, each pixel or block has its corresponding depth value. For example, an object near a viewer has a greater depth value than an object far from the viewer. As a result, in a depth-map image, the object near the viewer is brighter than the object far from the viewer. In another embodiment, the depth map may be provided, for example, by a depth generator (e.g., 10 in
Subsequently, in step 33, the depth map or maps from the depth generator 22 are enhanced by a depth enhancer 23 to modify or improve depth characteristics of the image(s). In the embodiment, depth histogram stretching is performed on the depth map from the depth generator 22. The depth histogram is a distribution (usually depicted as a graph) of the depth levels of pixels, in which each depth level has its counted number of pixels. If the histogram is depicted as a graph, the horizontal axis represents the depth levels and the vertical axis represents the corresponding number of pixels.
In a specific embodiment, the depth histogram stretching may be performed by applying a gain on each depth level. In another specific embodiment, the depth histogram stretching may be performed by applying a transformation (or mapping) characterized by a curve (e.g., a gamma curve) on the depth levels of a depth histogram.
Afterwards, in step 34, the enhanced depth map (or maps) from the depth enhancer 23 are fed to a depth-image-based rendering (DIBR) unit 24, which generates (or synthesizes) an enhanced left (L′) image 25A and an enhanced right (R′) image 25B according to the enhanced depth map(s) and the original left (L) image and the right (R) image. The resulting enhanced left image and enhanced right image may then be displayed by a 3D imaging system. The DIBR unit 24 may be implemented by a suitable conventional technique, for example, disclosed in a disclosure entitled “A 3D-TV Approach Using Depth-Image-Based Rendering (DIBR),” by Christoph Fehn, the disclosure of which is hereby incorporated by reference.
If the depth enhancement is to be performed globally, a global depth histogram is then generated, in step 63A, according to the entire depth map. Subsequently, in step 64A, the global depth histogram is enhanced, for example, by S-curve transformation (or mapping) on the depth levels of the global depth histogram, as exemplified in
If the depth enhancement is to be performed locally, a number of local depth histograms are then respectively generated, in step 63B, according to divided depth maps of the received depth map.
Although specific embodiments have been illustrated and described, it will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims.
