Patent Publication Number: US-7907151-B2

Title: Apparatus and method for associating non-overlapping visual objects with z-ordered panes

Description:
BRIEF DESCRIPTION OF THE INVENTION 
     This invention relates generally to rendering visual objects. More particularly, this invention relates to organizing visual objects for optimization when rendering a document. 
     BACKGROUND OF THE INVENTION 
     Handling overlapping visual objects is an ongoing problem in rendering graphics. Overlapping visual objects can bloat file sizes and lengthen rendering times. There are existing optimization functions that can be used on groups of non-overlapping objects to minimize file size and rendering time. In view of this, it would be advantageous to provide a function that groups the visual objects, while retaining correct z-order, into sets of non-overlapping objects so that file size and rendering time optimizations man be used. 
     SUMMARY OF INVENTION 
     The invention includes a computer readable storage medium with executable instructions to accept a set of document objects, wherein each document object is associated with a z-order. A document object in the set of document objects is passed to a pre-rendering region comprising a stack of one or more panes, wherein the document object is added in z-order. The document object is checked against each pane in the stack for document object overlap, beginning with a topmost pane, until a pane selected from one of a bottommost pane and an overlap pane is reached. The document object is associated with a pane selected from one of the bottommost pane and a pane above the overlap pane. The pane above the overlap pane is selected from one of a pane in the stack and a new pane added to the top of the stack. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The invention is more fully appreciated in connection with the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates a computer constructed in accordance with an embodiment of the invention. 
         FIG. 2  illustrates processing operations associated with an embodiment of the invention. 
         FIG. 3  illustrates a document object layout associated with an embodiment of the invention. 
         FIG. 4  illustrates an initial pane of the pre-rendering region configured in accordance with an embodiment of the invention. 
         FIG. 5  illustrates a stack of panes including the initial pane of  FIG. 4  configured in accordance with an embodiment of the invention. 
         FIG. 6  illustrates a stack of panes including the stack of panes of  FIG. 5  configured in accordance with an embodiment of the invention. 
         FIGS. 7A ,  7 B and  7 C illustrate individual panes associated with a stack of panes processed in accordance with an embodiment of the invention. 
     
    
    
     Like reference numerals refer to corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The following terminology is used while disclosing embodiments of, the invention: 
     A document object is a piece of visible content (e.g., a portion of text, a visualization, a header or footer, a table, a watermark, a graphic) in a document. 
     A pane is a virtual layer in a document rendering. A pane is associated with one or more non-overlapping document objects. The level of a pane in a stack of panes determines whether its associated objects appear above or below objects in other panes that overlap them in the document rendering. 
     An overlap pane is a pane containing a document object that is configured to be partially or entirely covered by a document object with a higher z-order value. 
     A pre-rendering region is a stack of one or more panes comprising a temporary document. The pre-rendering region is typically stored in a volatile memory location and its contents are not maintained after the document has been rendered to its new location. The pre-rendering region is not visible to a user. 
     Z-order is the sequence of overlapping two-dimensional objects such as windows in a Graphical User Interface or document objects in a report. When two objects overlap, the z-order determines which object should appear on top of the other. The object with the higher z-order appears on top. 
       FIG. 1  illustrates a computer  100  configured in accordance with an embodiment of the invention. The computer  100  includes standard components, including a central processing unit  102  and input/output devices  104 , which are linked by a bus  106 . The input output devices  104  may include a keyboard, mouse, touch screen, monitor, printer, and the like. A network interface circuit  108  is also connected to the bus  106 . The network interface circuit (NIC)  108  provides connectivity to a network (not shown), thereby allowing the computer  100  to operate in a networked environment. 
     A memory  110  is also connected to the bus  106 . In an embodiment, the memory  110  stores one or more of the following modules: a layering module  112  and a rendering module  114 . The layering module  112  accepts document objects, checks for overlap of document objects and associates them with layered panes. The rendering module  114  renders the layered document objects in their specified order, optimizing for render time, file size and the like. 
     The executable modules stored in memory  110  are exemplary. An operating system module and a Graphical User Interface (GUI) module may be included. It should be appreciated that the functions of the modules may be combined. In addition, the functions of the modules need not be performed on a single machine. Instead, the functions may be distributed across a network, if desired. Indeed, the invention may be implemented in a client-server environment with various components being implemented at the client-side and/or the server-side. It is the functions of the invention that are significant, not where they are performed or the specific manner in which they are performed. 
       FIG. 2  illustrates a high level workflow  200  associated with an embodiment of the invention. The first processing operation is for the layering module  112  to accept a set of document objects  202 . The layering module  112  then passes one document object at a time to the topmost pane of a pre-rendering region  204 . The layering module  112  checks to see if the document object overlaps with any document objects already associated with the current pane  206 . If the document object does not overlap another document object,  206 —No, and the current pane is not the bottommost pane,  208 —Yes, the document object is passed to the pane below the current pane  210 . The layering module  112  checks for overlap with document objects on that pane  206 . If the document object does not overlap another document object,  206 —No, but there are no other panes below the current pane (i.e., the current pane is the bottommost pane),  208 —No, then the layering module associates the document object with the current (bottommost) pane  212  and passes the next document object to the topmost pane  204 . 
     If the document object does overlap another document object in the current pane,  206 —Yes, and there is a pane above the current pane (i.e., the current pane is not the topmost pane)  214 —Yes, then the layering module  112  associates the document object with the pane above the current pane  216  and passes the next document object to the topmost pane  204 . 
     If the document object overlaps another document object in the current pane,  206 —Yes, and there is not a pane above the current pane (i.e., the current pane is the topmost pane),  214 —No, then the layering module  112  creates a new pane and adds it to the top of the stack of panes  218 . Then the layering module  112  associates the document object with the new topmost pane  220  and passes the next document object to the topmost pane  204 . The workflow completes when there are no more document objects available. 
     In an embodiment, overlap detection is facilitated by an interval array along the y-axis of each pane. An interval array is an array that records intervals of the y-axis that contain document objects. Each pane in the pre-rendering region has its own interval array which tracks all document objects associated with its pane and all panes below it. A potential overlap occurs when a document object is inserted and its span intersects with a known span. At that point, the document objects that contribute to the y-axis span(s) of the interval array are checked against the incoming document object to see if there is overlap on both the x-axis and y-axis spans. That is, the document objects are checked to see if they actually overlap. If not, then the document object is added to the list of document objects, and the interval array&#39;s span is modified accordingly (for example, if a document object is partially within the span, the span on the interval array may grow). The span update may cause multiple spans to merge. 
       FIG. 3  illustrates the layout of a set of document objects (e.,g., text, charts, tables, maps, watermarks, graphics)  301 - 305  in a document (erg., a report, a text file, a spreadsheet, a diagram)  300  associated with an embodiment of the invention. It this example, each document object  301 - 305  has an increasing z-order as a function of its numeric value. Thus, document object  301  has the lowest z-order and document object  305  has the highest. 
       FIG. 4  illustrates a pane  400  containing document objects  301  and  302  of  FIG. 3  configured in accordance with an embodiment of the invention. The pane  400  is the initial pane of the pre-rending region. As non-overlapping document objects are passed to the pre-rendering region, they are associated with the initial pane  400 . Here, document objects  301  and  302  are associated with the initial pane  400 . In an embodiment, the first document object  301  is automatically associated with the initial pane  400 . 
       FIG. 5  illustrates a set of panes  500  including the pane  400  of  FIG. 4 . In an embodiment, when the document object  303  is passed to the pre-rendering region, it is found to overlap the document object  302  and a new pane  502  is created. The document object  303  is then associated with the new pane  502 . The document object with the next highest z-order  304  is passed to the topmost pane  502  of the pre-rendering region. Because the document object  304  does not overlap any document objects associated with the pane  502 , it is passed to the pane  400  below. The document object  304  does not overlap any document objects in the pane  400 , and the pane  400  is the bottommost pane, so the document object  304  is associated with the pane  400 . 
       FIG. 6  illustrates a set of panes  600  including the pane  400  of  FIG. 4  and the pane  502  of  FIG. 5 . When the document object  305  is passed to the topmost pane of the pre-rendering region  502 , it is found to overlap the document object  303 . A new topmost pane  602  is created and the document object  305  is associated with it. 
       FIGS. 7A ,  7 B and  7 C illustrate the resulting panes  400 ,  502  and  602  and their respective associated document objects. It should be noted that each pane is associated with a set of non-overlapping document objects: pane  400  with document objects  301 ,  302  and  304 ; pane  502  with document object  303 ; and pane  602  with document object  305 . 
     The groups of non-overlapping objects are rendered to their destination location (e.g., a screen, a metafile, a vector image, a Portable Document Format file, a text file, a bitmap, a printer) in order of their associated panes, e.g., the bottommost pane is rendered first and the topmost pane is rendered last. In an embodiment, the implemented optimization functions may render the document objects associated with a single pane in order of document object type (e.g., text, chart, table, map, watermark, graphic) or document object properties (e.g., size, font, color, style, transparency, language). 
     In an embodiment, the z-order indicates the pane layer of a document object. In this case, overlap is detected prior to receiving the set of document objects and thus. overlap does not need to be detected again. One pane is created for each z-order and all document objects associated with that z-order are associated with the equivalent pane. 
     An embodiment of the present invention relates to a computer storage product with a computer-readable medium having computer code thereon for performing various computer-implemented operations. The media and computer code may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well known and available to those having skill in the computer software arts. Examples of computer-readable media include, but are not limited to: magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD-ROMs, DVDs and holographic devices; magneto-optical media; and hardware devices that are specially configured to store and execute program code, such as application-specific integrated circuits (“ASICs”), programmable logic devices (“PLDs”) and ROM and RAM devices. Examples of computer code include machine code, such as produced by a compiler, and files containing higher-level code that are executed by a computer using an interpreter. For example, an embodiment of the invention may be implemented using Java, C++, or other object-oriented programming language and development tools. Another embodiment of the invention may be implemented in hardwired circuitry in place of, or in combination with, machine-executable software instructions. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that specific details are not required in order to practice the invention. Thus, the foregoing descriptions of specific embodiments of the invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed; obviously, many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, they thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the following claims and their equivalents define the scope of the invention.