Abstract:
Audiovisual content presentation to users has evolved from users receiving hardcopy printed materials to their searching and retrieving information by accessing any of hundreds of millions of web sites and billions of web pages. User retrieval being performed on a wide variety of platforms from high performance PCs to low performance cellular telephones. Accordingly substantial limitations exist in initially displaying this audiovisual content as well as when users dynamically manipulate browser dimensions or move through the content. Further additional limitations exist for those authoring both online and traditional content to manipulate sourced content to provide the published content. As such a requirement exists for dynamically resizing images that respects the information content within the audiovisual content. Embodiments of the invention provide for content aware resizing of audiovisual content both within authoring and user environments, and in dependence upon device characteristics such as display, processor, power, etc.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of co-pending U.S. patent application Ser. No. 12/691,765 filed Jan. 22, 2010. The aforementioned related patent application is herein incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to image processing and more specifically to content aware image re-dimensioning. 
       BACKGROUND OF THE INVENTION 
       [0003]    In the last fifteen years or so accessing, generating and exchanging information has fundamentally shifted for Governments, commercial enterprises, private and public organizations, and the general public. In those fifteen or so years the Internet has gone from a niche application to an essential element of the lives of most individuals in the developed world. As of Jul. 1, 2009 it was estimated that the number of Internet users had exceeded 1.67 billion people out of a world population of approximately 6.8 billion, i.e. 25% of the world&#39;s population. These users are accessing information contained in approximately 22 billion pages hosted on over 110 million websites (http://www.domaintools.com/internet-statistics). 
         [0004]    Over the same period of time how the Internet is accessed has shifted dramatically as well. No longer are users sitting at desktop personal computers (PCs) in front of 15″ or 17″ CRT displays interfaced to large metal cases hosting for example a single Intel®  486  processor operating 50 MHz or 100 MHz with 32 MB memory with a 16 GB hard-drive accessing dial-up connectivity at 56 kb/s. Today their desktop PC is most likely to be a laptop PC working alone or in conjunction with a LCD display of dimension 17″, 19″, 21″, etc up to 32″ or more for graphical designers allowing them to unplug and move to another location to continue working This laptop for example containing an AMD Athlon™ Dual-Core 2.00 GHz processor with 4 GB memory, a 500 GB hard-drive, and with Internet connectivity at 5 Mb/s, 10 Mb/s or more through wireless WiFi (IEEE 802.11) or WiMAX (IEEE 802.16) interfaces. 
         [0005]    Additionally a multitude of other portable electronic devices now provide their users with Internet access including for example personal digital assistants (PDAs) and cellular telephones (e.g. Apple iPhone, Research in Motion&#39;s Blackberry, Palm Pre, Samsung Chocolate), gaming consoles (e.g. Microsoft Xbox, Nintendo DSi, Nintendo Wii), and audiovisual media players (e.g. Apple iPod). Accordingly users can access the Internet essentially anywhere and anytime with one of several devices they typically posses. Further recent device developments such as the Apple iPhone® with integrated silicon MEMS devices allow for dynamic rotation of the mobile device display between landscape and portrait formats as the user rotates their device. Further, operating systems such as Microsoft&#39;s Windows and Apple&#39;s MAC OS X allow users to dynamically change the size and effective orientation of web pages on their computers, and newer introductions such as Microsoft Window 7 allow users to dynamically move and display directly content from their laptop PC to another device such as another laptop, television, PDA etc. 
         [0006]    As a result the original consideration of images on mobile devices as simply wallpaper and screen savers or web site content as being displayed on large portrait orientated PC displays has been destroyed. Audiovisual content posted to the Internet within any web page is dynamically accessed, dynamically adjusted, and is highly manipulated. A news image may be accessed within seconds by millions of users with displays from typical cellular telephone 240×320 and 320×480 pixel displays of 2.S″ or 3.2″ through to IS″ or 17″ displays of 1920×1080p supporting HDTV and above to 32″, 42″ LCD, plasma displays, and projectors as users employ their televisions as monitors. 
         [0007]    Further users expectations have increased during this time. Applications such as Microsoft Word and Corel WordPerfect have evolved from being simple word processing applications to entry level desktop publishing suites supporting graphics and audiovisual content and the generation of web pages. At the same time desktop publishing software has expanded to facilitate direct handling of XML, HTML languages, multiple interfaces to digital audio, digital photo, and digital video applications and allowing direct publication in printed formats, secured digital content, and web content. 
         [0008]    However, despite all these advances the content published onto Internet web pages is in the vast majority of cases fixed, even from leading content providers such as Yahoo and Google. Hence, as the viewing user adjusts the dimensions of their web page, for example allowing them to view the Internet content whilst working on another application without having to move from one application to another, then essentially their web page acts similar to a window adjusting the amount of the web page they can view but the audiovisual content is typically fixed in size. In the other cases, for example Google image search, the content is adjusted to a limited extent according to the dimensions of the web browser page, for example the number of images across the web browser page changes. However, the image sizes remain constant and the user must now scroll further to view all the images and move to the next page. In others the page layout adjusts to display the text according to the web browser page size but again the dimensions of the image have been fixed. Today image manipulation in respect of adjusting displayed dimensions of an image is essentially limited to the desktop publisher&#39;s domain when generating the web page content. The user&#39;s ability to control the display of the web page content is limited to either adjusting the web browser page size or adjusting the zoom that the web browser displays content with. 
         [0009]    It would be beneficial for audiovisual content presented to a user to be dynamically displayed according to a variety of factors including but not limited to the dimensions of the web browser page, image display device dimensions, and image display device resolution for example. In this manner disadvantages of the prior art that will become evident in the descriptions of these approaches will be removed. 
         [0010]    Amongst the earliest prior art techniques for image adjustment to reflect a change in displayed dimensions is cropping, such as shown in  FIG. 1 , where two desktop publisher snapshot images  100  and  150  are shown. First desktop publisher snapshot image  100 , from Adobe Photoshop Lightroom® shows an image of a bride  110  together with a cropped highlighted region  120  which the user will select as the cropped image to employ. Similarly second desktop publisher snapshot image  150 , from Adobe Photoshop shows a cityscape  160  together with a cropped cityscape region  170  which the user has selected as the cropped image to employ. Second desktop publisher snapshot image  150  also has icon  180  that projects an automatically generated mask onto the cityscape  160  at either a predetermined pixel count or physical dimension. However, this prior art approach only works to reduce an image dimension, it cannot scale the image up, and if automatically generated may remove significant content in the image. Cropping does not scale the source image even when reducing the displayed dimensions and has typically been limited to date therefore to desktop publishing. 
         [0011]    Within the prior art there are many approaches to automate the cropping operation by detecting content and cropping in dependence of the content. Examples include A. T. Schowkta in U.S. Pat. No. 7,133,050 entitled “Automated Image Resizing and Cropping”, Suh et al in “Automated Thumbnail Cropping and its Effectiveness (UIST&#39;03 Proc. 16th ACM Symposium User Interface Software and Technology, ACM Press, New York, pp. 95-104, 2003), A. Santella et al in “Gaze-Based Interaction for Semiautomatic Photo Cropping” (Proc. SIGCHI Conference on Human Factors in Computing Systems, pp. 771-780, 2006) and E. G. Callway in US Patent 2007/0,152,990 entitled “Image Analyzer and Adaptive Image Scaling Circuit and Methods”. 
         [0012]    Within the prior art such cropping methodologies have been employed in conjunction with linear and non-linear scaling methodologies to provide images of variable size. Linear and non-linear scaling allows the generation of images that are both larger and smaller than the original whilst cropping adjusts the image content. Such a non-linear technique being shown in  FIG. 2  by resizing tool window  200 , as provided by SB Software (Nonlinear Image Resizing Tool, Version 1.0, www.sb-software.com). As shown within resizing tool  200  an original image  210  of dimensions 747×923 pixels has been selected for resizing to resized image  220  of dimensions 1024×768 pixels representing an aspect ratio change from 0.81:1 to 1.33:1. As indicated by resizing setting toolbar  230  the user can apply nonlinear factors that range from squeezing the centre of the image and stretching the edges of the image through to the reverse of stretching the centre of the image and squeezing the edges of the image. Such a non-linear scaling whilst an improvement over linear scaling in many instances can still result in unnatural images, particularly as the human visual process is highly sensitive to distortion and non-linearity. 
         [0013]    Extensions of this technique to reduce such visual irregularities and reduce the user perceptions that image manipulation has been undertaken have included A. Soroushi in U.S. Pat. No. 7,355,610 entitled “Method and Apparatus for Expanding Image Data to Create Enlarged Images for Display”, Y-H. Lee in US Patent Application 2007/0,147,708 entitled “Adaptive Image Size Conversion Apparatus and Method Thereof’, and C-H. Chou in US Patent Application 2007/0,104,394 entitled “Method and System for Digital Image Magnification and Reduction.” However, such whilst addressing the automation aspect of dynamically adjusting images to different display devices or varying web browser page dimensions they have drawbacks in terms of requiring significant processing complexity even if they can be implemented in the firmware of devices or require additional specific hardware. 
         [0014]    It would be apparent that a requirement for a solution addressing high volume consumer applications of image display would be beneficially provided without requiring additional hardware and in a software I firmware form that operates within a wide range of portable devices with varying processing capabilities. Further such firmware should beneficially operate rapidly to provide real time image resizing and with low power consumption to extend the portable device lifetime to the user. Such a focus within the prior art is typically absent as most prior art applications have focused to desktop publishing type applications such as Adobe Photo shop, Corel PhotoShop, Microsoft PowerPoint, and Microsoft Publisher for example wherein the user is primarily authoring and generating content for publication either in physical or online media formats. Referring to  FIG. 3  there is presented an image scaling flow according to the prior art of S-H Lee in US Patent Application 2008/0,019,439 entitled “Apparatus and Method for Low Distortion Display in a Portable Communication Terminal”. As shown in first step  300 A an image  310  has been received by a portable device, not shown for clarity, for display that requires resizing. Accordingly the process of Lee divides the image  310  in second step  300 B to a plurality of image segments  321  through  327  in preparation for applying the transformation to each image segment  321  through  327 . In third step  300 C a linear or non-linear scaling is applied to each image segment  321  through  327  thereby generating scaled image segments  331  through  337 . The scaling applied to each of image segment  321  through  327  to generate scaled image segments  331  through  337  being different such that the content is scaled to an increased percentage of the image to be displayed to the user but is done so in a manner that is supposed to reduce perceived distortion. 
         [0015]    However, Lee applies a predetermined scaling according to a mathematical function, for example a cosine function, such that weighting in the scaled image is given to the central portion of the content which is expanded and the outer portions are reduced when the overall image is to be reduced dimensionally. Whilst other mathematical functions may be employed such as a sine, hyperbolic tangent, sinc etc for example the appropriate mathematical function should be determined by the content of the image which requires in an automatic scaling application, that the image be first processed to determine the distribution of content and hence appropriate function to apply. Equally, Lee only teaches applying the function in one dimension whereas it would be beneficial to provide the methodology in two dimensions when considering the target portable devices etc. Other examples within the prior art include P. O. Vale in U.S. Pat. No. 7,385,615 entitled “System and Method for Scaling Images to Fit a Screen on a Mobile Device According to a Non-Linear Scale Factor”. 
         [0016]    A further alternative is taught by H. Chao et al in US Patent Application 2008/0,095,470 entitled “Digital Image Auto-Resizing” and shown schematically in  FIG. 4  as applied to an initial image  410 . As shown Chao teaches that the image is broken into two portions, a first portion  420  where the content will be scaled at a first scaling factor, and a second portion  440  which will be scaled at a second scaling factor. 
         [0017]    Accordingly first portion  420  is broken into four elements, first to fourth elements  421  through  424  respectively, which will be scaled to fit the new overall window to present the scaled image  460  but is performed in a manner to reduce the reduction in the portion of the scaled image given to the second portion  440 . Hence, first element  421  and fourth element  424  would be scaled only in the horizontal axis whilst second element  422  and third element  423  would be scaled only in the vertical axis. As such the scaled replicas of first to fourth elements  421  through  424  respectively are combined to form scaled first portion  430 . The second portion  440  is scaled to generate scaled second portion  450  and is then combined with scaled first portion  440  to generate the scaled image  460  to be presented to the user. Again a drawback of Chao is that selecting the portions of the image, namely first and second portions  420  and  440  respectively, can significantly impact the resultant scaled image  460  and the viewer&#39;s perception or satisfaction as a result. Other examples of such blocked scaling of images include K. Berkner et al in U.S. Pat. No. 7,548,654 entitled “Header Based Scaling and Cropping of Images Compressed Using Multi-Scale Transforms” and S J. Kaasila et al in U.S. Pat. No. 7,287,220 entitled “Methods and Systems for Displaying Media in a Scaled Manner and/or Orientation”. 
         [0018]    Extensions of such cutting, scaling and re-pasting include those reported by V. Setlur et al in “Automatic Image Re-Targeting” (Proc. 18th ACM Symposium on User Interface Software and Technology, pp. 153-162, 2005), J. Jia et al in “Drag-and-Drop Pasting” (Proc. SIGRAPH 2006, Vol. 25, No. 3, pp. 631-637July 2006), J. Wang et al in “Simultaneous Matting and Compositing” (Microsoft Technical Report MSR-TR-2006-63, May 2006), C. Jacobs et al in “Adaptive Grid-Based Document Layout” (Proc. ACM SIGGRAPH, pp. 838-847, 2003), W. T. Freeman et al in U.S. Pat. No. 6,919,903 entitled “Texture Synthesis and Transfer for Pixel Images”, and I. Clarke et al in US Patent Application 2006/0,072,853 entitled “Method and Apparatus for Resizing Images.” 
         [0019]    A further extension of this approach within the prior art was described by B. S. Hallberg et al in U.S. Pat. No. 6,563,964 entitled “Image Down-Sampling Using Redundant Pixel Removal” wherein the image to be reduced in size was non-uniformly down-sampled to remove aliasing within the high spatial frequency information content such that low spatial frequency information content is preferentially removed. This required that the image be processed by a spatial frequency estimator that compared groups of pixels in order to produce a classification of the image. Subsequently a path generator and path scorer analyze potential deletion paths within the image and the path with highest score, the one giving minimal distortion and aliasing, is selected for pixel removal. This process being repeated until a desired number of image rows and/or columns have been removed. As such Hallberg teaches that the entire image is arbitrarily analyzed rather than the preceding prior art wherein sampling of the image for determination of scaling was predetermined by applying a mask, template or mathematical function. However, Hallberg as noted only addresses reduction and is primarily focused to the problem of reducing the display of textual based information such as directory listings etc in applications such as Windows Explorer as the display type varied rather than arbitrary window generation as users adjust web browser pages etc. 
         [0020]    The approach of Hallberg was extended by S. Aviden et al as reported in U.S. Pat. No. 7,477,800 entitled “Method for Re-Targeting Images” and their publication “Seam Carving for Content Aware Image Resizing” (ACM Transactions on Graphics SIGGRAPH 2007, Volume 26, Number 3, Article 10, July 2007). Aviden coined the term “seam carving” to refer to a simple image operator that provides adjustment of an image&#39;s size by carving-out or inserting pixels in different parts of the image. The determination of “seams” to carve or insert being made in respect of an energy function that defines the importance of pixels. A “seam” being defined by a connected path of low energy pixels crossing the image from one side to another representing the minimum energy path across the image. Removal of these “seams” providing for reduction in the image dimension in horizontal and/or vertical dimensions whilst insertion of these “seams” providing for expansion of the image. Aviden states that the image operator produces, in effect, a content-aware resizing of the image. 
         [0021]    Additional extensions of this work have been reported by M Klingemann (see flash blog http://www.quasimondo.com/archives/000652.php of September 2007) using an energy function generated through convolving the image with a blurred offset version of itself, the offset being a few pixels. H. Welles has also published open source implementations of the “seam carving” method of Aviden (see Ariadne and Seamstress algorithms at http://seam-carver.sourceforge.net). 
         [0022]    Aviden teaches that the digital image to be dimensionally adjusted is initially converted into a so-called “energy map” wherein every pixel in the image is mapped to a pixel within the “energy map,” Subsequently the cumulative energy for a continuous I-pixel wide “seam” is calculated from one side of the image to the other side. The two preferred energy functions taught are outlined below in Equations 1 and 2. Aviden teaches that no single energy function works well across all images but that most have similar ranges of resizing before visual artifacts are introduced. 
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         [0000]    where I(x, y) is a particular pixel, and HoG (I(x, y)) is taken to be a histogram of orientated gradients at every pixel (see N. Dalal et al “Histograms of Orientated Gradients for Human Detection” Intl. Conf. Computer Vision and Pattern Recognition, Vol. 2, pp 886-893). Aviden teaches using an 8-bin histogram computed over an 11×11 window around a pixel for HoG(I(x, y)). 
         [0023]    Referring to  FIG. 5  the method of A divan is presented using images taken from the publication “Seam Carving for Content Aware Image Resizing” (ACM Transactions on Graphics SIGGRAPH 2007, Volume 26, Number 3, Article 10, July 2007). A source image  510  is shown, and the intention is to change the aspect ratio from say 4:3 to 16:9. Applying a conventional linear scaling to source image  510  results in linear image  520 . Applying the method of “seam carving” of Aviden begins with the generation of the “energy map”  530  from source image  510 . From this single “energy map” a horizontal seam map  540  is generated together with vertical seam map  550  that define the cost of removing a seam in each direction. Based upon the determination to remove either a horizontal and/or vertical seam a carved image  560  is generated. If the carved image  560  is not at the target image size then the process cycles back to recalculate the energy map  530  and repeats until the final image dimension is achieved. 
         [0024]    Aviden teaches that resizing an image from 240×320 pixels to 128×160 pixels, such as reflects an image shifted from the inner display of a Blackberry Pearl Flip cellular telephone to it&#39;s outer display, would be achieved by removing 112 vertical ‘seams’ and 160 horizontal “seams”. Removal of each seam requires that the “energy map” is recalculated to determine which “seam” is to be removed next. Accordingly the removal of the 112 vertical and 160 horizontal “seams” requires the generation of 272 “energy maps” which is computationally intense, particularly so if Equation (2) was employed. As such Aviden teaches that a designer may author a multi-size image once and a client application depending upon the image size needed performs the requisite number of “seam” removals or additions such that the resizing can occur quickly in real time to fit the layout or display. The authoring being the computationally intense generation of the large number of “energy maps” and processing of the “seam” determinations to generate the multiple image sizes. The information relating to the multiple image sizes would for example be stored as a header within the image file. Such an approach of header encoding being taught, albeit not in relation “seam carving” for example by K. Berkner in U.S. Pat. No. 7,548,654 as outlined supra. 
         [0025]    However, a user accessing the Internet and retrieving images is not going to only access images generated by publishers with desktop publishing software that included the “seam carving” information for multiple images embedded within. Further such an approach also affects even the retrieval of audiovisual content by increasing the file size. As of mid-2009 the indexable web contained at least 22 billion pages (http://www.worldwidewebsize.com) hosted on over 110 million websites (http://www.domaintools.com/internet-statistics). Simply searching using Google for images with “photo” returns over 700 million results whilst popular social networking websites such as Facebook are reported at peak times to have 300,000 images uploaded a second by registered members. It would be evident that even if “seam carving” was introduced into all image generating devices, such as desktop publishing software, digital cameras, cellular telephones etc, by virtue of being embedded as part of an international standard such as Portable Network Graphics (PNG), Tagged Image File Format (TIFF), and Motion Pictures Expert Group (MPEG) for example, that it would take a significant period of time to become the dominant format for digital audiovisual content accessible to Internet users. 
         [0026]    Accordingly it would be beneficial to provide a method of resizing digital images that was independent of their method of generation, i.e. portable consumer electronics or desktop software, independent of the platform upon which the images were to be displayed, i.e. low cost consumer portable devices or laptop computers, the display they are to be displayed upon, i.e. 128×160 pixel 1.8″ cellular telephone display, 1600×900 pixel 17.3″ laptop, user activity such as flipping the Apple iPhone from a 320×480 pixel portrait orientation to 480×320 pixel landscape orientation in a fraction of a second, and the source image format. 
         [0027]    It would be further beneficial if the method of resizing was also content aware, i.e. provided scaling that did not remove significant image elements or distort images at typical resizing factors unless expressly permitted by the user. Such permission being provided within desktop publishing or image manipulation software such as Abode Photo shop, Corel Paint Shop Pro, Ulead Photo Impact for example. It would be further beneficial if the method permitted the protection of content during resizing or explicitly weighted content for removal during resizing or editing, was fast, and easily incorporated into the firmware of devices as well as desktop publishing software. 
       SUMMARY OF THE INVENTION 
       [0028]    It is an object of the present invention to obviate or mitigate at least one disadvantage of the prior art. 
         [0029]    In accordance with an embodiment of the invention there is provided a computer implementable method comprising the steps of generating at least one saliency map of a plurality of saliency maps, the at least one saliency map characterized by at least a number of pixels equal to a number of pixels within a source audiovisual content and each pixel within the at least one saliency map having a value associated with it which is determined in dependence upon determining at least a saliency for the corresponding pixel within the source audiovisual content, and generating at least one reduced saliency map of a plurality of reduced saliency maps, each reduced saliency map associated with a saliency map and generated by applying at least one predetermined scaling factor to the at least one saliency map. The method further comprising the steps of applying a path determination process to the at least one reduced saliency map, the path determination process for identifying a sequence of pixels within the at least one reduced saliency map that meet a predetermined condition, and modifying the source audiovisual content in dependence upon at least the sequence of pixels. 
         [0030]    In accordance with another embodiment of the invention there is provided a computer implementable method comprising the steps of generating a saliency map characterized by at least a number of pixels equal to a number of pixels within a source audiovisual content and each pixel within the saliency map having at least two values associated with it, one value determined in dependence upon at least a saliency for the corresponding pixel within the source audiovisual content along a first axis of the image and the other value determined in dependence upon at least a saliency for the corresponding pixel within the source audiovisual content along a second axis of the image and generating a reduced saliency map by applying at least one predetermined scaling factor to the saliency map, each pixel with the reduced saliency map having at least first data generated in dependence upon at least the one value of a pixel within the saliency map associated with the pixel in the saliency reduced map and second data generated in dependence upon at least the other value of a pixel within the saliency map associated with the pixel in the saliency reduced map. The method further comprising the steps of applying a path determination process to at least one of the first data and the second data within the reduced saliency map, the path determination process for identifying a sequence of pixels within the reduced saliency map that meet a predetermined condition, and modifying the source audiovisual content in dependence upon at least the sequence of pixels. 
         [0031]    In accordance with another embodiment of the invention there is provided a device comprising:
   (a) an interface for receiving audiovisual content for presentation to a user upon a display forming a predetermined portion of the device, the audiovisual content characterized by at least a source dimension being at least one of a physical dimension and a number of pixels; and   (b) a circuit including at least a processor and a memory for executing a series of processes, the processes including at least:
       (i) a display process for determining a target dimension for the audiovisual content for presentation to the user; and   (ii) an image process for generating a modified image in dependence upon at least the audiovisual content, the target dimension, and the at least a source dimension, the image process comprising the steps of:   (1) generating a saliency map characterized by at least a number of pixels equal to a number of pixels within the source audiovisual content and each pixel within the saliency map having at least two values associated with it, one value determined in dependence upon at least a saliency for the corresponding pixel within the source audiovisual content along a first axis of the image and the other value determined in dependence upon at least a saliency for the corresponding pixel within the source audiovisual content along a second axis of the image;   (2) generating a reduced saliency map by applying at least one predetermined scaling factor to the saliency map, each pixel with the reduced saliency map having at least first data generated in dependence upon at least the one value of a pixel within the saliency map associated with the pixel in the saliency reduced map and second data generated in dependence upon at least the other value of a pixel within the saliency map associated with the pixel in the saliency reduced map;   (3) applying a path determination process to at least one of the first data and the second data within the reduced saliency map, the path determination process for identifying a sequence of pixels within the reduced saliency map that meet a predetermined condition; and   (4) modifying the audiovisual content in dependence upon at least the sequence of pixels to generate display audiovisual content.   
       
 
         [0040]    Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0041]    Embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein: 
           [0042]      FIG. 1  is a representation of the prior art wherein software provides image resizing through cropping; 
           [0043]      FIG. 2  is a representation of the prior art where image resizing is based upon a non-linear scaling; 
           [0044]      FIG. 3  depicts image resizing according to the prior art of S-H Lee in US Patent application 2008/0,019,439; 
           [0045]      FIG. 4  depicts image resizing according to the prior art of H. Chao in US Patent application 2008/0,095,470; 
           [0046]      FIG. 5  depicts content aware image resizing according to the prior art of S. Aviden in U.S. Pat. No. 7,477,800; 
           [0047]      FIG. 6  depicts an embodiment of the invention depicting generation of the first gradient maps and associated reduced second gradient maps with their reuse in repeated removal of selected pixel paths to resize an image; 
           [0048]      FIG. 7  A depicts an embodiment of the invention in establishing a pixel path within a gradient map; 
           [0049]      FIG. 7B  depicts an embodiment of the invention in establishing a pixel path within a gradient map; 
           [0050]      FIG. 7C  depicts repeated pixel path determinations made upon the reduced second gradient map according to an embodiment of the invention for reduced processing complexity and improved speed; 
           [0051]      FIG. 7D  depicts a process flow wherein repeated pixel path determinations are made upon the second saliency map according to an embodiment of the invention for reduced processing complexity and improved speed; 
           [0052]      FIG. 8  depicts an embodiment of the invention wherein pixel path selection is determined from different second reduced gradient maps which are derived from a common first gradient map; 
           [0053]      FIG. 9  depicts an embodiment of the invention wherein pixel path selection is made within a second reduced gradient map and interpolated for image adjustment during image resizing; 
           [0054]      FIG. 10  depicts a limitation within the prior art of S. Aviden in U.S. Pat. No. 7,477,800 wherein seam carving removes pixels with significant image content; 
           [0055]      FIG. 11  depicts an embodiment of the invention within an authoring environment wherein significant image content is protected from selection in the pixel path determinations for image resizing; 
           [0056]      FIG. 12  depicts results of prior art linear scaling and an embodiment of the invention wherein a portion of a person&#39;s body is protected during the image resizing; 
           [0057]      FIG. 13  depicts an embodiment of the invention within an authoring environment wherein image content is preferentially selected in the pixel path determinations for image resizing; 
           [0058]      FIG. 14  depicts an embodiment of the invention wherein within an authoring environment image content is identified by the user as being preferentially removed and protected in the pixel path determinations and image resizing; 
           [0059]      FIG. 15  depicts a process flow according to an embodiment of the invention wherein pixel path determination is executed upon a portable device in dependence upon characteristics of the portable device; 
           [0060]      FIG. 16  depicts multiple pixel selection within image resizing according to an embodiment of the invention based upon the reduced second gradient map; 
           [0061]      FIG. 17  depicts an embodiment of the invention wherein pixel path determination based upon the reduced second gradient map is performed within a video authoring or display environment; and 
           [0062]      FIG. 18  depicts protection of image content from selection during pixel path determination within image resizing according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0063]    The present invention is directed to content aware resizing of audiovisual and image content. 
         [0064]    Reference may be made below to specific elements, numbered in accordance with the attached figures. The discussion below should be taken to be exemplary in nature, and not as limiting of the scope of the present invention. The scope of the present invention is defined in the claims, and should not be considered as limited by the implementation details described below, which as one skilled in the art will appreciate, can be modified by replacing elements with equivalent functional elements. 
         [0065]    Reference below is made in respect of  FIGS. 6 through 14  and  FIGS. 16 through 18  to an authoring environment in respect to the discussion, such as for example a desktop publishing environment. The scope of the present invention should not be considered as limited by these implementation details, as one skilled in the art will appreciate, which can be modified such that embodiments of the invention may operate with or without user intervention or may be employed in display and presentation environments to a user, such as described in  FIG. 15 . 
         [0066]    Further in  FIG. 15  reference is made to a portable device in the determination of the parameters in establishing aspects of the resizing operation which extend beyond the intended image size. The scope of the present invention should not be considered as limited by these application details, as one skilled in the art will appreciate, which can be varied according to the particular portable device but also apply to the wider range of devices upon which user activities may require content aware image resizing. 
         [0067]    Within the background to the invention discussed supra descriptions of  FIGS. 1 through 5  have been included and are not repeated here. 
         [0068]    Referring to  FIG. 6  there is depicted an exemplary flow according to an embodiment of the invention. As shown a source image  610  is provided for which a resizing operation is required within an authoring environment, the authoring environment omitted for clarity. The content aware resizing process then generates first horizontal saliency map  620  and first vertical saliency map  625  which represent the horizontal and vertical saliencies within the image which are determined from Equations 3 and 4 below: 
         [0000]      Saliency horizontal ( n   ij )=| I ( n   i,j+1 )|−| I   (   n   i,j−1 )|  (3)
 
         [0000]      Saliency vertical ( n   i,j )=| I ( n   i+1,j )−|( I ( n   i−1,j )|  (4)
 
         [0000]    where I(n i,j ) is the intensity of the i th , j th  pixel in the image. 
         [0069]    Each of the first horizontal saliency map  620  and first vertical saliency map  625  are then scaled to generate second reduced horizontal saliency map  630  and second reduced vertical saliency map  635 . These are then employed to generate the cost functions for removing a pixel seam in each of the horizontal and vertical directions. A selected vertical seam from second reduced horizontal saliency  630  is shown as pixel path  645  projected onto resizing image  640 . Removal of the pixels identified by pixel path  645  would reduce the horizontal dimension of the source image  610 . Alternatively insertion of replica pixels identified by pixel path  645  would increase the horizontal dimension. Accordingly the source image  610  is scaled based upon a pixel path that is determined through the scaling transformation in respect of the horizontal and vertical saliencies defined in Equations (3) and (4) supra. 
         [0070]    Referring to  FIG. 7  A there is depicted a process flow  700 A according to an embodiment of the invention in establishing a pixel path within a reduced saliency map. The process starts with first pixel map  710 A of dimension 5×3, which represents a subset of a reduced saliency map such as second reduced horizontal saliency map  630  or second reduced vertical saliency map  635  in  FIG. 6  supra. The process then determines the interconnected paths between the pixels on the first row and the second that are connected, resulting in second pixel map  720 A which shows this connectivity between the first row and second row such that the process then sums these paths giving the middle summation in third pixel map  730 A together with the mapping of connectivity between the summed second row and third row. The resultant summation being shown in fourth pixel map  735 A along with the connectivity paths from each row to the next. According to an embodiment of the invention process flow  700 A is set to detect the minimum summation in the pixel path and thereby determines this is in the summed path provided in fifth pixel map  740 A. Accordingly the pixels within the subset of the saliency map are selected as depicted by sixth pixel map  745 A. In the final step the process removes these pixels thereby generating seventh pixel map  750 A which is now of dimension 4×3. In the process according to the embodiment of the invention this pixel removal in the reduced saliency map follows removal of pixels within the audiovisual content, such as described below in respect of  FIG. 15 . 
         [0071]    It would evident to one skilled in the art that process flow  700 A does not take into account the pixels removed from the saliency map such as is evident in the comparison of sixth and seventh pixel maps  745 A and  750 A respectively where simply the pixel path selected has been removed. In other embodiments of the invention, for instance where a portion of the saliency map has a localized reduction in saliency compared with the overall saliency map the reduction algorithm may perform some form of compensation such as shown below in Table 1. As shown on the left is seventh pixel map  750 A according to process flow  700  in  FIG. 7 . On the right is a compensated pixel map representing the same pixel path removal but where now pixels adjacent the removed pixel are re-calculated according to Equations SA and SB below: 
         [0000]        S   k+l ( i− 1 ,j )= S   k ( i− 1 ,j )+ S   k ( i,j )/ 2   (5A)
 
         [0000]        S   k+1 ( i− 1 ,j )= S   k ( i+ 1 ,j )+ S   k ( i,j )/ 2   (5B)
 
         [0000]    where S k  (i, j) represents the saliency value at the i th , j th  pixel for step k in the image resizing process. It would be apparent that similar equations as Equations 5A and 5B exist for removing a horizontal pixel path. Such a compensated pixel map locally increases saliency above the initially calculated values upon removal of a pixel path which would weight a subsequent pixel path determination away from the same region of the saliency map such that multiple pixel path determinations do not always run through the same portion of the saliency map and hence the original image. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Left: Saliency map after pixel path removal according to process 
               
               
                 700 of FIG. 7A Right: Saliency map after pixel path 
               
               
                 removal with compensation as discussed supra 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 3 
                 5 
                 4 
                 7 
                 3 
                 5 
                 4 
                 8 
               
               
                   
                 7 
                 1 
                 9 
                 8 
                 7 
                 1 
                 11.5 
                 10.5 
               
               
                   
                 6 
                 9 
                 7 
                 8 
                 6 
                 9 
                 7 
                 9 
               
               
                   
                   
               
             
          
         
       
     
         [0072]    It would be evident to one of skill in the art that the selected path within process  700 A by virtue of having the lowest summation of saliencies represents a path of pixels that have low difference in intensity to their neighbouring pixels in a particular direction. These pixels are not necessarily at a minimum within the reduced saliency map for the other direction and hence not necessarily the same pixels as would be selected in the process of A vidan when employed on the same image. As such removing these pixels from the image should not significantly affect the content for the user whilst allowing the image dimension to be reduced. It would evident to one skilled in the art that zero saliency or very low saliencies may reflect areas of consistent intensity rather than lack of content. As such regions where saliencies exceed a predetermined threshold may be subjected to a second process to determine whether they are simply pixels reflecting low intensity variations and hence sacrificial content or significant content of consistent intensity. For example the second process may be to calculate and compare a second saliency for a particular pixel, see for example Equations 5C and 5D below; with the first saliency such that upon a precondition being met the calculated saliency is replaced with a predetermined value. 
         [0000]      Saliency2 horizontal ( n   i,j )=| I ( n   i,j+n )|−| I ( n   i,j−n )|  (5C)
 
         [0000]      Saliency2 horizontal ( n   i,j )= dI ( i,j )/ dj   (5D)
 
         [0073]    Referring to  FIG. 7B  there is depicted a process flow  700 B according to an embodiment of the invention in establishing a pixel path within a reduced saliency map. The process starts with first pixel map  710 B of dimension 5×3, which represents a subset of a reduced saliency map such as second reduced horizontal saliency map  630  or second reduced vertical saliency map  635  in  FIG. 6  supra. The process then determines the interconnected paths between the pixels on the first row and the second that are connected, resulting in second pixel map  720 B which shows this connectivity between the first row and second row such that the process then sums these paths giving the middle summation in third pixel map  730 B together with the mapping of connectivity between the summed second row and third row. The resultant summation path being shown in fourth pixel map  735 B along with the connectivity paths from each row to the next. According to an embodiment of the invention process flow  700 B is set to detect the maximum summation in the pixel path and thereby determines this is in the summed path provided in fifth pixel map  740 B. Accordingly the pixels within the subset of the saliency map are selected as depicted by sixth pixel map  745 B. In the final step the process adds these pixels into the first pixel map  710 B thereby generating seventh pixel map  750 B which is now of dimension 6×3. 
         [0074]    It would be evident to one of skill in the art that the selected path within process  700 B by virtue of having the highest summation of saliencies represents a path of pixels that have high difference in intensity to their neighbouring pixels. As such replicating those pixels within the image that relate to those within the reduced saliency map should preserve the visually significant content for the user whilst allowing the image dimension to be increased. 
         [0075]    It would be apparent to one skilled in the art that the pixel path selection in  FIGS. 7  A and  7 B may be subject to additional constraints or determined on alternative basis. For example it may be a constraint that the pixel path originates within a predetermined distance of the image edge such that the central image content is preserved irrespective of its pixel saliency summation, where the assumption is that most significant content is within the central portion of the image. Alternatively a summation may be performed over predetermined regions of the second saliency map such that regions of higher than average accumulated saliency are identified and preserved. Optionally the pixel path selection when the adjustment is a significant percentage of the original image dimension may be established such that pixel paths should be maximized in one direction and minimized in another. Similarly where pixel path selection has been described as seeking a minimum/maximum the converse of seeking the maximum/minimum for the same image resizing operation exists. Many alternatives exist within the scope of the invention. 
         [0076]    Referring to  FIG. 7C  there is depicted a process flow  700 C wherein repeated pixel path determinations are made upon the reduced second saliency map according to an embodiment of the invention for reduced processing complexity and improved speed. As such within process  700 C a first reduced saliency map  710 C is shown, equivalent for example to first pixel maps  710 A and  710 B of  FIGS. 7  A and  7 B respectively or predetermined portions of second reduced horizontal saliency map  630  or second reduced vertical saliency map  635  in  FIG. 6  supra. First reduced saliency map  710 C is a 8×5 array of reduced saliency data, being either the horizontal saliency or vertical saliency of that localized region of the image as reduced saliency map  710 C is a reduced dimensional matrix of the corresponding first saliency map, for example first horizontal saliency map  620  or first vertical saliency map  625  as disclosed in  FIG. 6 . As such a pixel within first reduced saliency map  710 C represents N pixels, wherein N represents the scale reduction applied to the corresponding first saliency map. Saliency S(i, j) may alternatively be defined for example by Equations 6 and 7 below rather than by Equations 3 and 4. 
         [0000]    
       
         
           
             
               
                 
                   
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         [0000]    where I(i, j) represents the intensity of the ith, r pixel in the source image. 
         [0077]    In first pixel summation map  720 C the summed saliency values S(i, j) from each pixel within the top row to the bottom row are shown for connected paths. Also shown is first pixel path  725 C selected from the first pixel summation map  720 C, in this case based upon the lowest sum. The pixels within the image content being resized and first reduced saliency map  710 C corresponding to the first pixel path  725 C are then removed resulting in second reduced saliency map  730 C, i.e. pixels S(1,4)=2, S(2,4)=1, S(3,4)=1, S(4,4)=2, and S(5,5)=5 are removed. Corresponding pixels in the image are removed that correspond to the selected pixels in first pixel path  725 C thereby reducing the image width based upon its content. Using second reduced saliency map  730 C the summation process is repeated and second pixel summation map  740 C is generated. Again a pixel path  745 C is established such that the corresponding pixels within the second reduced saliency map  730 C are removed, i.e. pixels S(1,1)=1,S(2,2)=3,S(3,1)=3,S(4,1)=3, and S(5,1)=4. Again corresponding pixels in the reduced image from the previous removal of pixels are removed, further reducing the width of the image. 
         [0078]    Removal of the selected pixels in second reduced saliency map  730 C results in third reduced saliency map  750 C. As above the process then generates third pixel summation map  760 C and selects the next pixel path  765 C. Applying the selected path to third reduced saliency map  750 C results in fourth reduced saliency map  770 C of dimensions 5×5 i.e. removing pixels S(1,3)=3, S(2,2)=3,S(3,3)=1, S(4,2)=3, and S(5,2)=5. As such it would be evident to one skilled in the art that the reduction of the image is accomplished without recalculating the reduced saliency maps from the corresponding horizontal saliency map or vertical saliency map, such as horizontal saliency map  630  and vertical saliency map  640  in  FIG. 6 . As such scaling the image is achieved with a significant reduction in the processing complexity when compared with the prior art of content aware image resizing, such as S. Aviden et al who recalculate the top level pixel maps from the resultant image after each “seam” is carved or inserted. Such a reduction in processing complexity beneficially provides for the pixel path methodology to be deployed within portable consumer electronics with reduced processing capabilities when compared to laptop PCs with dual-core 2 GHz processors and 4 GB RAM. 
         [0079]    It would be apparent to one of skill in the art that the pixel path adjustment provided within each of the image content and saliency maps as a result of pixel path determination within the reduced saliency map may not always remove the corresponding number of pixels within these higher plane maps, such as described below in  FIG. 16 . It would be apparent that image resizing may require an increase/decrease in a number of pixels that does not match an integer scaling ratio, i.e. a prime number, which requires either the saliency mapping be performed with a scaling equal to the prime number, not be scaled, or be left at a size not matching the target. Considering simply resizing involving between 1 and 1000 pixels there are 168 prime numbers. For example, removing 367 pixels may be achieved with 367 single pixel path removals which is time consuming but leads to the desired result. 
         [0080]    Alternatively as described in embodiments of the invention the scaling provides an increased speed, for example 183 removals of 2 pixel wide paths, 92 removals of 4 pixel wide paths, 61 removals of 6 pixel wide paths, or  37  removals of 10 pixel wide paths. In all cases the final image is at the incorrect final dimension. Accordingly it would be apparent that providing the process with the ability to removal a number of pixels within the image content that does not match the scaling allows the final image to be scaled in a content aware manner to the correct final dimension. Accordingly, 36 removals of 10 pixel wide path with a ÷10 scaling may be followed by a final 7 pixel wide leaves the image at the target resize dimension. Similarly applying 36 removals of 6 pixel wide paths followed by a final single wide pixel path. Accordingly the process may dynamically select a scaling to meet the requirements for speed and processing whilst achieving the final target dimension. 
         [0081]    Referring to  FIG. 7D  there is depicted a process flow  700 D wherein repeated pixel path determinations are made upon the second saliency map according to an embodiment of the invention for reduced processing complexity and improved speed. As such within process  700 D a first reduced saliency map  710 D is shown, equivalent for example to first pixel maps  710 A and  710 B of  FIGS. 7  A and  7 B respectively or predetermined portions of second reduced horizontal saliency map  630  or second reduced vertical saliency map  635  in  FIG. 6  supra. First reduced saliency map  710 D is a 8×5 array of reduced saliency data, being either the horizontal saliency or vertical saliency of that localized region of the image as reduced saliency map  710 C is a reduced dimensional matrix of the corresponding first saliency map, for example first horizontal saliency map  620  or first vertical saliency map  625  as disclosed in  FIG. 6 . As such a pixel within first reduced saliency map  710 D represents effectively N pixels, wherein N represents the scale reduction applied to the corresponding first saliency map. 
         [0082]    In first pixel summation map  720 D the summed saliency values S(i, j) from each pixel within the top row to the bottom row are shown for connected paths. Also shown is first pixel path  725 D selected from the first pixel summation map  720 D, in this case based upon the lowest sum. The pixels within the saliency map, not shown for clarity but being that from which first reduced map  710 D was derived, corresponding to the first pixel path  725 D are then removed. The resulting saliency map, also now shown for clarity, is then reduced to yield second reduced saliency map  730 D, of dimensions 7×5, which whilst globally similar to first reduced saliency map  710 D as only a portion of the pixels were removed differs in those pixels identified by region  735 D, i.e. pixels S(1,4)=4,S(2,4)=6, and S(3,4)=2. As discussed supra the corresponding pixels in the image were also removed in addition to those within the saliency map corresponding to the selected pixels in first pixel path  725 D thereby not only reducing the image width but doing so based upon its content. The process flow  700 D then uses second reduced saliency map  730 D to repeat the summation process from which second pixel summation map  740 D is generated. Again a pixel path  745 D is established based upon the minimum saliency summation and the process flow  700 D then removes corresponding pixels within both the image and saliency map. From this resulting modified saliency map, not shown for clarity process flow  700 D calculates the third reduced saliency map  750 D. 
         [0083]    Third reduced saliency map  750 D of dimensions 6×5 is again globally similar to second reduced saliency map  730 D, as only a portion of the pixels within the saliency map were removed which forms the source of third reduced saliency map  750 D, but differs in region  755 D which differs now in S(3,1)=6,S(4,1)=5, and S(5,1)=6. Again process flow  700 D performs another summation process resulting in third pixel summation map  760 D and selects the next pixel path  765 D having lowest saliency summation. Applying this selected path to both the image and saliency map as discussed supra further reduces the image width based upon its content and results in a new saliency map, not shown for clarity, from which a fourth reduced saliency map  770 D, now of dimensions 5×5 is generated. As the dimensions of the reduced saliency map reduces the region that differs from the preceding reduced saliency map increases typically. As such, now region  775 D now differs in 
         [0000]        S (1,3)=5 ,S (1,4)=6 ,S (2,3)=7 ,S (2,4)=7 ,S (3,3)=4 ,S (3,4)=5 ,S (4,2)=4 ,S (4,3)=5, and  G (5,3)=7 
         [0084]    As such it would be evident to one skilled in the art that the reduction of the image is accomplished according to the embodiment of the invention presented in  FIG. 7D  without recalculating the saliency maps from the corresponding image. However, unlike the preceding embodiment in  FIG. 7C  the reduced saliency maps are calculated from the applicable horizontal saliency map or vertical saliency map, such as horizontal saliency map  620  and vertical saliency map  625  in  FIG. 6 , which is reduced during the process. As such scaling the image is achieved with a significant reduction in the processing complexity when compared with the prior art of content aware image resizing, such as S. Aviden et al who recalculate the top level pixel maps from the resultant image after each “seam” is carved or inserted. 
         [0085]    Optionally the pixel path selected is based upon multiple conditions. For example, the pixel path selected is not only one meeting a minimum summation or a maximum summation such as presented supra in respect of  FIGS. 7  A and  7 B but is one where the pixel path is one with a low summation and results in the minimum change in an overall measure of the reduced saliency map for example. 
         [0086]    Considering portable devices today with significant market share within their respective markets such as Research in Motion&#39;s popular Blackberry 8100, 8300 and 8700 series cellular telephones employing an Intel PXA901 processor at 312 MHz with 16 MB RAM, Nintendo&#39;s DSi handheld game console employs two ARM processors, an ARM9E processor operating at 133 MHz and an ARM7TDMI coprocessor operating at 33 MHz, with the ARM9E processor controlling game play and image processing, and Apple&#39;s iPod portable audiovisual media players series including the Nano and 40 which employ dual 80 MHz ARM 7TDMI processors. All of these devices support Internet access and hence would benefit from dynamic image processing when browsing the Internet as their capabilities are increased. As such embodiments of the invention support use within portable consumer devices to dynamically resize image with content aware scaling in real-time thereby allowing them to access any published audiovisual or image content already in existence without requiring preprocessing by desktop publishing software suites and increased file sizes to handle the header embedded seam carving sequence such as taught by S. Aviden. 
         [0087]    It would be evident to one skilled in the art that the path selection step resulting in third pixel path  765 C could have selected from four potential paths, 
         [0000]        S (1,3)→ S (2,2)→ S (3,3)→ S (4,2)→ S (5,1); S (1,3)→ S (2,2)→ S (3,3)→ S (4,2)→ S (5,2); S (1,3)→ S (2,2)→ S (3,3)→ S (4,3)→ S (5,2); S (1,3)→ S (2,2)→ S (3,3)→ S (4,2)→ S (5,4).
 
         [0000]    Optionally the pixel path content aware image resizing process may have secondary routing protocols that establish which of these to select preferentially. For example the secondary protocol may be to avoid vertical pixel combinations wherever possible, thereby removing S(1,3)→S(2,2)→S(3,3)→S(4,3)→S(5,2) as an option, or seeks to remove pixels at the edge of the image thereby favoring S(1,3)→S(2,2)→S(3,3)→S(4,2)→S(5,1). 
         [0088]    Referring to  FIG. 8  there is depicted according to an embodiment of the invention image process flow  800  wherein pixel path selection is determined from one of two different second reduced saliency maps, being first and second reduced saliency maps  820  and  830  respectively, wherein each second saliency map is derived from a common first saliency map  810 . According a source image  805  provides the pixel intensity array I(i, j) that acts as the source data for calculating Saliency horizontal (n i,j ) and Saliency vertical  which form the basis of horizontal saliency map  810 A and vertical saliency map  810 B. This step in the process flow being common to two users, one on a laptop computer  860  and another on a cellular telephone  870 . The process in execution upon the laptop computer  860  generates a first pair of reduced saliency maps  830  which are then used to generate dynamically scaled first and second resized images  840  and  850  as the user adjusts the onscreen dimensions of a web browser whose content includes the source image  805 . 
         [0089]    In contrast the process in execution upon a cellular telephone  870  generates a second pair of reduced saliency images  820  that are then used to generate third resized image  880 . Accordingly the process runs on the two different devices in a manner that adjusts to suit the device upon which it is executing. It would be evident to one skilled in the art that a resizing operation geared to a 240×320 pixel 2.1″ cellular telephone  870  display has different requirements to one displaying images upon a 17″ 1920×1080 display on a laptop computer  860 . As a result the process according to embodiments of the invention allows for content aware image resizing that is configurable to the device upon which the process is operating. This configurable processing is not contained within the prior art content aware resizing approaches discussed supra. 
         [0090]    Now referring to  FIG. 9  there is depicted a flow  900  according to an embodiment of the invention wherein pixel path selection is made within a second reduced saliency map and interpolated for image adjustment during image resizing. As such there is shown a source image  910  upon which a resizing operation is to be performed, the intensity data I(i, j) of which is employed in generating first saliency map  920  from which second reduced saliency map  930  is generated. The second reduced saliency map  930  is then the data source for the pixel path determination process, such as presented supra in respect of  FIGS. 7  A,  7 B and  7 C. A pixel path portion  940  of the determined pixel path  935  from second reduced saliency map  930  is shown comprising a 4×4 matrix with selected pixels  945  infilled. Within this example scaling between first saliency map  920  and second reduced saliency map  930  is a factor of 3. As such pixel path portion  940  is scaled back by a factor of 3 to generate expanded pixel path  950  within which selected pixels  945  are shown as highlighted pixels  955 . 
         [0091]    Next flow  900  executes an interpolation process to generate interpolated pixel map  960  wherein the selected pixels  955  are shown together with interpolated pixels  964 . Next each selected pixel  955  and interpolated pixel  964  are replaced by pixel path element  972  which are determined as the average of each neighbouring pixel  974 , i.e. P(i, j)=(I(i−1, j)+I(i+1, j))/2. The pixel path elements  972  are then inserted into the original image  910  to generate resized image  980 . It would be evident that within  FIG. 9  the flow  900  described relates to an increase in image dimensions as opposed to a reduction. Accordingly the process described in  FIGS. 7C and 7D  supra for selecting sequential paths and removing them to reduce a dimension may be applied in reverse and multiple pixel paths inserted into the image. Accordingly rather than the saliency maps and reduced salience maps decreasing in dimension they would increase. It would evident to one skilled in the art that generation of pixel path elements  972  may be varied, such as for example rather than using the average of neighbouring pixels the value inserted is that representing the pixel with the minimum value between the neighbouring pixels  974  and interpolated pixel  964 . 
         [0092]    Now referring to  FIG. 10  there is depicted a limitation within the prior art of S. Aviden in U.S. Pat. No. 7,477,800 wherein seam carving removes pixels with significant image content. As shown a source image  1010  is presented that contains a first region  1015  of very little variation, being an item of clothing for one of the two individuals within the source image  1010 . The prior art of S. Aviden was employed by W. Wedler for this source image  1010  (see Image Resizing by Seam Carving—Project 2—Computational Photography at Carnegie Mellon University, http://www.cs.cmu.edu/afs/andrew/scs/cs/15-463/f07/proj2/www/wwedler). Shown in second image  1020  are multiple seams  1025  determined for an image reduction process wherein a majority of the multiple seams  1025  run through the first region  1015  As a result when these seams are removed to generate resized image  1030  the first region  1015  is removed preferentially resulting in second region  1035  which has essentially removed the majority of the torso of the individual within the image. As discussed supra in respect of  FIG. 7  A an automated resizing process upon a device may having generated a first saliency map or second reduced saliency map according to the invention have identified that a substantial region within the map that had low saliency, namely first region  1015 , such that pixel paths would preferentially pass through it, for example by comparing saliencies calculated using for example Equation (3) with either Equation (5C) or (5D), or through another process. In these circumstances either replacing saliencies with a predetermined value such that these pixels were not preferentially selected or removing paths calculated through these pixels would result in retention of such a region. 
         [0093]    Within a desktop publishing application such a restriction may be made using a mask applied to the second reduced saliency map from which the pixel paths are selected. Such an approach according to an embodiment of the invention within an authoring environment is shown in  FIG. 11  wherein there is depicted a process flow  1100  establishing a pixel path within a saliency map, subsequently referred to as pixel maps. The process starts with first pixel map  1110  of dimension 5×3, which represents a subset of a saliency map such as second reduced horizontal saliency map  630  or second reduced vertical saliency map  635  in  FIG. 6  supra for example. The process then determines the interconnected paths between the pixels on the first row and the second, resulting in second pixel map  1120  which shows this connectivity between the first row and second row. However, S(1,5)=|I(i, j+1)−I(i, j−1)|=2 for example, has been masked, shown by hatching in that cell in first and second pixel maps  1110  and  1120  respectively. As such the connectivity mapping between the first and second rows does not include S(2,5)→S(1,5) such that when the process sums these paths giving the middle summation in third pixel map  1130  this path is not calculated or mapped. Third pixel map  1130  also showing connectivity mapping between the summed second row and third row. The resultant summation path for the 5×3 array being shown in fourth pixel map  1135  along with the connectivity paths from each row to the next. According to an embodiment of the invention process flow  1100  is set to detect the minimum summation in the pixel path and thereby determines this is in the summed path shown in fifth pixel map  1140 . 
         [0094]    The selected path as shown in fourth pixel map  1140  being S(1,1)→S(2,2)→S(3,1) whereas in  FIG. 7  A supra using the same pixel map, without the masking applied to S(1,5), the path selected was S(1,5)→S(2,4)→S(3,5). Accordingly the pixels within the subset of the saliency map are selected as depicted by sixth pixel map  1145  which are then removed by the process to generate seventh pixel map  1150  which is now of dimension 4×3 with S(1,5)=2 still protected for subsequent pixel map operations. It would be evident that rather than limiting the connectivity mapping aspect of the process flow that alternatively the saliency value stored may be replaced with a saliency value that would remove the pixel from summed routes. For example where the pixel path process seeks a minimum summation making the protected pixels have high saliency would remove then from the pixel path selection, similarly where the pixel path process seeks a maximum summation making the protected pixels have low saliency would remove then from the pixel path selection. Other options would be apparent to one of skill in the art. 
         [0095]    Referring to  FIG. 12  there are depicted the results of prior art linear scaled  1220  and an embodiment of the invention in content aware scaled image  1230  as applied to an original image  1210 . In linear scaled  1220  the woman&#39;s face is distorted whereas by protecting this portion  1205  of the original image  1210  the content aware scaled image  1230  has a woman with a longer body as desired but with a natural head proportion. 
         [0096]    In other authoring applications it may be appropriate to remove content preferentially. Such a process  1300  is depicted in  FIG. 13  according to an embodiment of the invention. The process starts with first pixel map  1310  of dimension 5×3, which represents a subset of a saliency map such as second reduced horizontal saliency map  630  or second reduced vertical saliency map  635  in  FIG. 6  supra for example. The process then determines the interconnected paths between the pixels on the first row and the second that are connected, resulting in second pixel map  1320  which shows this connectivity between the first row and second row. However, whilst connectivity S(2,2)→S(1,1) represents a lower summation than S(2,2)→S(1,2) the process  1300  forces this connectivity so that pixel S(1,2) is contained within the calculated summations. S(1,2)=|I(i, j+1)−I(i, j−1)|=5 for example, has been masked, shown by shading in that cell in first and second pixel maps  1310  and  1320  respectively. As such the connectivity mapping continues to third pixel map  1330  showing connectivity mapping between the summed second row and third row. The resultant summation path for the 5×3 array being shown in fourth pixel map  1335  along with the connectivity paths from each row to the next. According to an embodiment of the invention process flow  1300  is set to detect the minimum summation in the pixel path and thereby determines this is in the summed path provided in fifth pixel map  1340 . 
         [0097]    The selected path as shown in fourth pixel map  1340  being S(1,2)→S(2,2)→S(3,1) whereas in  FIG. 7  A supra using the same pixel map without the masking to S(1,S) being applied the path selected was S(1,S)→S(2,4)→S(3,5). Accordingly the pixels within the subset of the saliency map are selected as depicted by sixth pixel map  1345  which are then removed by the process to generate seventh pixel map  1350 . It would be evident that rather than limiting the connectivity mapping aspect of the process flow that alternatively the saliency value stored may be replaced with a saliency value that would removes the pixel from summed routes. For example where the pixel path process seeks a minimum summation making the preferred pixels have low saliency, i.e. zero, would preferentially weight to these pixels in pixel path selection, similarly where the pixel path process seeks a maximum summation making the protected pixels have high saliency would remove then from the pixel path selection. Other options would be apparent to one of skill in the art. Such options may in some circumstances force the pixel path selection to these pixels even when local pixel paths may have had summations that previously weighted path selection to them. 
         [0098]    Now referring to  FIG. 14  there is depicted an embodiment of the invention wherein within an authoring environment image content within a source image  1410  is identified by the user as being both preferentially removed and protected in the pixel path determinations and image resizing. Accordingly in first image  1420  the user has selected the far left individual for removal with first removal mask  1422 , but being conscious of the middle left individual and the background tower has protected these with first and second protection masks  1424  and  1426  respectively. Then applying a content aware image resizing process according to an embodiment of the invention yields first output image  1430  wherein the selected individual has been removed but the overall content has minimal artifacts to indicate to a viewer that the image was processed. 
         [0099]    An alternate authoring is shown in second image  1440  where the user has selected the far right individual for removal with second removal mask  1442 , but being conscious of the middle right individual and the background building has protected these with third and fourth protection masks  1424  and  1426  respectively. Then applying a content aware image resizing process according to an embodiment of the invention yields second output image  1450  wherein the selected individual has been removed but the overall content has minimal artifacts to indicate to a viewer that the image was processed. 
         [0100]    It was noted supra that a content aware image resizing process according to embodiments of the invention may be deployed within a range of electronic devices including portable devices allowing the process to resize images retrieved by users rather than requiring all images they access be authored in a suite providing header encoded seam carving sequences such as taught within the prior art by S. Aviden. Referring to  FIG. 15  there is depicted a process flow  1500  according to an embodiment of the invention wherein pixel path determination for content aware image resizing is executed upon a portable device in dependence upon characteristics of the portable device. As such the process begins at step  1502  where the user opens a web browser interface, or accesses the Internet and retrieves a web page through a specific Internet access application such as the browsers within Blackberry and iPhone PDAs rather than Windows Internet Explorer, Mozilla, etc. As such in step  1504  they access a web page and as part of that digital content relating to an image is downloaded in step  1506 . The application in execution upon the user&#39;s electronic device establishes the display dimensions for the downloaded image in step  1508  and then in step  1510  retrieves device settings relating to the portable device the user is using, not shown for clarity. 
         [0101]    Subsequently in step  1512  the image scaling ratio required for the image is determined and then, based upon the device settings and image, scaling the scaling ratio of the reduced saliency pixel map is determined in step  1514 . Next in step  1516  the horizontal saliency map 1H is generated, and subsequently in step  1518  the vertical saliency map IV is calculated. These together with the scaling ratio of the saliency maps determined in step  1514  are used to calculate horizontal reduced saliency map 2H and vertical reduced saliency map 2V in steps  1520  and  1522 . In step  1524  a counter is set, X=1, and in step  1526  applicable pixel paths within reduced saliency horizontal and vertical maps 2H(X) and 2V(X) respectively are determined. Next in step  1528  these pixel paths are scaled as appropriate, such as discussed supra in respect of  FIG. 9  and then an interpolation is performed in step  1530  to establish the applicable horizontal and/or vertical seams. In step  1532  these interpolated pixels are replaced by “proper” pixels which are generated using the neighboring pixels according to a predetermined algorithm. 
         [0102]    This determined pixel seam is then applied to the image in step  1534  and the pixel path is then applied to the saliency maps 1H(X) and 1 V(X) as appropriate in step  1536 . Then in step  1538  the process determines whether the image size required has been achieved, which if it has results in the process moves to step  1542  and terminating. If further resizing is required the process moves to step  1540 , increments the counter, X=X+1, and loops back to step  1520  so that the process can continue such as described for example in respect of  FIG. 10 , which as outlined allows multiple pixel path selection without recalculation of the saliency energy map such as outlined supra. 
         [0103]    It would be evident to one skilled in the art that the characteristics of the portable device retrieved in the process flow and impacting the content aware resizing process may be other than display dimensions and may include but not be limited to processor speed, processor loading with other applications, graphics display driver settings, and battery status. For example, a low resolution display combined with a low processor speed may result in employing a high scaling ratio between saliency map and reduced saliency map whilst high resolution display and high processor speed may typically employ a low scaling ratio unless the battery status is of a low battery wherein minimizing processing may become more important such that a high scaling ratio IS again employed. Other combinations and eventualities would be evident to one of skill in the art. 
         [0104]    It would be apparent that under some circumstances it would be desirable to perform the pixel path based content aware resizing in a manner that is less precise or faster than described in respect of embodiments presented supra in respect of  FIGS. 6 through 15 . Referring to  FIG. 16  there is depicted a process  1600  wherein pixel path determination is made upon a reduced second saliency map according to an embodiment of the invention which is a variant of  FIG. 9  and provides reduced processing complexity and improved speed. Hence, as with the supra embodiments a source image  1610  is initially converted to a first saliency map  1620  which is then scaled, by a factor N, to provide reduced saliency map  1630 . The embodiment in  FIG. 16  does not specifically address horizontal and vertical versions of the first saliency map  1620  and reduced saliency map  1630  for simplicity. Accordingly as presented supra in respect of  FIG. 9  the process determines a pixel path  1640  comprising pixels  1645 , but now in generating scaled pixel path  1650  rather than discrete pixels being selected and the path interpolated the scaled pixel path has N×N pixels selected as groups  1655 , where N was the scaling ratio applied to the first saliency map, such that the pixel path is N pixels wide and continuous across the image. As such a single pixel path removal step removes N pixels in either the horizontal or vertical direction thereby reducing the processing by a factor of N. It would evident to one skilled in the art that the factor N as discussed supra in respect of  FIG. 8  may be dynamically determined based upon static characteristics of the device but also optionally dynamic aspects of the device such as processor load and battery status for example. 
         [0105]    Within the embodiments presented supra the consideration has been to digital content that relates to images and hence of a static content temporally unless resized by the activities of the user. However, it would be evident that the digital content accessed by users may include additionally audiovisual content such as downloaded or streamed according to international video standards such as Audio Video Interleave (AVI), Movie Picture Experts Group (MPEG, e.g. mp4), and Windows Media Video (WMV). Referring to  FIG. 17  there is depicted a process  1700  relating to multiple pixel path selection for content aware image resizing of audiovisual data. Hence there is shown an audiovisual sequence  1710  comprising a series of “frames”  1710 A through  1710 N. As first “frame”  1710 A is received it is converted to first saliency map  1720 A which is then converted to first reduced saliency map  1730 A as discussed supra in respect to other embodiments of the invention, and then the pixel path(s) is/are selected as shown in first path map  1740 A. Such a sequence may be repeated for each “frame” such as shown for N th  frame  1710 N wherein the Nth saliency map  1720 N is generated, converted to N th  reduced saliency map  1730 N resulting in Nth path map  1740 A. 
         [0106]    Such a process  1700  may exploit any of the adaptations identified within the preceding embodiments of the invention in  FIGS. 6 through 16  to adapt to the scenario of audiovisual content presentation and/or authoring. Optionally the same reduced saliency map may be applied for several “frames” to reduce processing complexity. It would be apparent that potentially allowing the content aware resizing to operate independently upon each “frame” may result in perceivable discontinuities. As such automated dynamic masking for protection/deletion of elements of the image such as discussed supra in respect of  FIGS. 11 through 14  may be considered. Such an automated processing for example being based upon recognizing an approximate repetitive feature in the saliency map or reduced saliency maps. Alternatively preference within a pixel path determination of a subsequent “frame” is weighted according to previous pixel paths. Such an approach being illustrated in  FIG. 18  where a first “frame”  1820  through generation of a first saliency map  1820  results in the selection of a first pixel path  1835  within first reduced saliency map  1830 . Processing of a subsequent “frame”  1840  through second saliency map  1850  and second reduced saliency map  1850  results in identification of second and third pixel paths  1862  and  1864  respectively. However, process  1800  applies a weighting to each of the second and third pixel paths which in this embodiment is determined pixel path  1835 . As shown second pixel path  1862  differs in 2 pixels selected but third pixel path  1864  differs in 8. Hence, the weighting for second pixel path  1862  would be higher as it matches more closely to first pixel path  1835  thereby lending to a reduction in visual discontinuities perceived by the viewer. 
         [0107]    It would be apparent to one skilled in the art that the embodiments presented supra have typically been described with an initial generation of a first saliency map and then the generation of a reduced saliency map. Alternatively the reduced saliency map may be generated without the storage or maintenance of the first saliency map. It would also be apparent that the scale between first saliency map and reduced saliency energy map has been presented as a constant within the above-described embodiments. Optionally the scale may be varied across the image, such non-linear scaling being optionally predetermined or established in dependence upon characteristics of the device displaying the image or content of the image. Alternatively the scaling may be varied between the vertical and horizontal directions of the image. 
         [0108]    In the above embodiments recalculation of the saliency map has been presented as occurring at the initialization of the process and that subsequently reduced saliency maps are employed in determining the pixel paths. It would be apparent to one skilled in the art that substantial image resizing may make it beneficial to perform a recalculation of the saliency map at a predetermined point in the process; this may optionally be a number of pixel seam adjustments or a percentage of the image adjustment for example. In the above embodiments discussion with respect to a particular format are for discussion purposes only as the embodiments are applicable to audiovisual content in multiple formats and multiple standards. 
         [0109]    In the above embodiments where adjustment of the process has been presented this has been considered primarily from the perspective of adjusting the process in dependence upon characteristics of the device upon which it is being executed. Optionally the process may be adjusted in respect to the audiovisual content itself, for example a different scaling process may be applied to JPEG files than is applied to TIFF files. 
         [0110]    In the above embodiments the process has been described by consideration of different saliency maps and reduced saliency maps for the horizontal and vertical aspects of the image resizing. It would be evident to one skilled in the art that the process may alternatively be performed with single reduced saliency “maps” (i.e. a three-dimensional arrays for example) wherein each pixel within each reduced saliency map for example is a different plan, i.e. G(i, j, k) such that for example k=1 represents the horizontal reduced saliency map and k=2 the vertical reduced saliency map. It would be evident that such an approach may be extended such that additional planes denoted by k relate to alternate saliency calculations, masking data for protection of content, masking data for denoting content to remove etc. 
         [0111]    The above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.