Patent Publication Number: US-2012044241-A1

Title: Three-dimensional on-screen display imaging system and method

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to digital image processing, and more particularly to a three-dimensional (3D) on-screen display (OSD) imaging system and method. 
     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). 
       FIG. 1A  shows a block diagram of a conventional 2D-to-3D imaging system  1 , which is capable of displaying on-screen display (OSD). A depth generator  10  creates depth information according to an original 2D image. The depth information is then processed by a depth-image-based rendering (DIBR) unit  12  to generate a left (L) image and a right (R) image. An OSD unit  14  is used to superimpose OSD on the left image and right image respectively, therefore resulting in a left image with OSD and a right image with OSD. Specifically speaking, the OSD unit  14 , at first, calculates binocular disparity between the left image and the right image, followed by superimposing the OSD on the left image and right image respectively.  FIG. 1B  schematically shows a left image with OSD  140 L and a right image with OSD  140 R. It is noted that the OSDs  140 L/ 140 R are superimposed on the left image and the right image with distinct disparity. For example, the OSD  140 L superimposed on the left image has a position slightly shifted to the left, while the OSD  140 R superimposed on the right image has a position slightly shifted to the right. 
     The conventional 2D-to-3D imaging system requires an effort (and associated cost) to calculate the binocular disparity. Further, while superimposing the OSD, the left image and the right image need be distinctly and respectively processed based on the calculated disparity. This leads to inefficient and inflexible performance for the conventional 3D imaging system. Accordingly, a need has arisen to propose a novel 3D OSD imaging system with more efficient and flexible scheme. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the embodiment of the present invention to provide a 3D OSD imaging system and method that are capable of generating the left image and the right image to be displayed on a 3D display in an efficient and cost-effective way, and are capable of flexibly setting the depth of the OSD region or regions. 
     According to one embodiment, a three-dimensional (3D) on-screen display (OSD) imaging system includes a depth generator, an image mixer, an OSD unit, a depth mixer and a depth-image-based rendering (DIBR) unit. The depth generator generates at least one image depth map according to a two-dimensional (2D) image. The image mixer superimposes an OSD image on the 2D image, thereby resulting in a 2D image with OSD, wherein the OSD image includes at least one OSD region. The OSD unit provides an OSD depth map and the OSD image. The depth mixer superimposes the OSD depth map on the image depth map, thereby resulting in a composite depth map. The DIBR unit generates a left image and a right image according to the 2D image with OSD and the composite depth map. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows a block diagram of a conventional 2D-to-3D imaging system; 
         FIG. 1B  schematically shows a left image with OSD and a right image with on-screen display (OSD); 
         FIG. 2  shows a block diagram that illustrates a 3D OSD imaging system according to one embodiment of the present invention; 
         FIG. 3  shows a flow diagram that illustrates a 3D OSD imaging method according to one embodiment of the present invention; 
         FIG. 4A  through  FIG. 4D  show some exemplary OSD depth maps; and 
         FIG. 5  shows an exemplary OSD region including two objects. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 2  shows a block diagram that illustrates a three-dimensional (3D) on-screen display (OSD) imaging system  2  according to one embodiment of the present invention.  FIG. 3  shows a flow diagram that illustrates a 3D OSD imaging method according to one embodiment of the present invention. 
     In the embodiment, the 3D OSD imaging system  2  includes a depth generator  20  that receives an original two-dimensional (2D) image and then accordingly generates at least one image depth map (step  31 ). In the depth map, each pixel or block of pixels has a corresponding depth value. For example, an object near a viewer has a greater depth value (or greater brightness value) than an object far from the viewer. 
     The 3D OSD imaging system  2  also includes an image mixer  22  that receives the original 2D image and an OSD image provided by an OSD unit  24 . The image mixer  22  then superimposes the OSD image on the original 2D image, therefore resulting in a 2D image with OSD (step  32 ). The OSD unit  24  provides the OSD image, for example, whenever a command is issued by a user or a host device such as a computer. The command controls an on/off status to turn on or turn off the display of the OSD. It is noted that the OSD image may include single OSD region or multiple OSD regions. 
     According to one aspect of the present embodiment, the OSD unit  24  further provides an OSD depth map (step  33 ). In the embodiment, the OSD information, which is retrieved from the command or a predetermined setting, includes spatial information and depth information. Specifically, the spatial information defines spatial characteristics, such as the shape, the size and/or the position, of each OSD region. The depth information sets the depth value within each OSD region. The OSD depth map is obtained based on spatial information and depth information. Generally speaking, the depth value of each pixel or block of pixels may be set individually.  FIG. 4A  through  FIG. 4D  show some exemplary OSD depth maps. Specifically,  FIG. 4A  shows a fixed-value depth map, according to which the pixels within the OSD region have the same depth value (e.g., D).  FIG. 4B  shows a horizontally gradient depth map, according to which the OSD region shows a gradient change (e.g., from D to D+4i) in the magnitude of the depth horizontally.  FIG. 4C  shows a gradient depth map similar to that of  FIG. 4B  except that the OSD depth map shows a gradient change (e.g., from D to D+4i) in the magnitude of the depth vertically.  FIG. 4D  shows a radiant depth map, according to which the depth values of the pixels within the OSD region increment (e.g., from D to D+4i) or decrement outwards. 
     In the embodiment, each OSD region may either be globally set (in a global mode) or be set in an object-oriented manner (in an object mode). Specifically, in the global mode, the depth of each OSD region is wholly set, for example, according to the OSD depth map exemplified in  FIG. 4A  through  FIG. 4D . In other words, each OSD region is considered as a single object. On the other hand, in the object mode, each OSD region includes a number of objects, and the depth for each object is set based on object property.  FIG. 5  shows an exemplary OSD region, which includes at least two objects  50  and  52 . The depth of the first object  50  is set distinctly from the depth of the second object  52 . For example, when the first object  50  is activated, for example, due to being selected by a user, the first object  50  is then set with a depth larger or smaller than the depth of the second object  52 . 
     According to a further aspect of the present embodiment, the 3D OSD imaging system  2  further includes a depth mixer  26  that receives the image depth map (from the depth generator  20 ) and the OSD depth map (from the OSD unit  24 ). The depth mixer  26  then superimposes the OSD depth map on the image depth map, therefore resulting in a composite depth map containing both the image depth and the OSD depth (step  34 ). Specifically speaking, the region excluding the OSD region(s) contains the image depth, and the OSD region or regions contain the OSD depth defined by the OSD depth map. 
     The 2D image with OSD (from the image mixer  22 ) and the composite depth map (from the depth mixer  26 ) are then fed to a depth-image-based rendering (DIBR) unit  28 , which generates (or synthesizes) a left (L) image and a right (R) image according to the 2D image with OSD and the composite depth map (step  35 ). The left image and the right image generated from the DIBR unit  28  contain OSD image with inherently existent binocular disparity between the left image and the right image. The DIBR unit  28  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. Conceptually, as described in this disclosure, the DIBR performs the following two-step process: at first, the original image points are re-projected into a 3D space (i.e., 2D-to-3D), utilizing the respective depth data; secondly, the 3D space points are projected into an image plane or planes (i.e., 3D-to-2D), which are located at the required viewing position respectively. The DIBR unit  28  may be implemented by hardware, software or their combination. It is appreciated by those skilled in the pertinent art that the depth mixer  26  may either be individually manufactured or be integrated with the DIBR unit  28 . For the latter case, the DIBR  28  receives the 2D image with OSD, the image depth map and the OSD depth map. 
     According to the embodiment described above, the resulting left image and the right image to be displayed on a 3D display may be generated in a more efficient and cost-effective way compared to the conventional 3D OSD system as shown in  FIG. 1A . Moreover, the depth of the OSD region or regions according to the present embodiment is programmable and may be more flexibly set compared to the conventional 3D OSD system as shown in  FIG. 1A . 
     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.