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Geometry Directed Browser for Personal Photographs

Center for Visual Information Technology

IIIT Hyderabad

Aditya Deshpande, Siddharth Choudhary, P J Narayanan,

Kaustav Kundu, Krishna Kumar Singh, Aditya Singh, Apurva Kumar

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We use SfM and other 3D computer vision techniques to provide intuitive Geometry Directed Photo Browsing.

Photo-Browsing

• Digital Photography

- No hard copy - Capture photographs and relive later on display device

• Photo-Browsers are tools to view digital photographs. E.g. Windows Photo Viewer, iPhoto, FSpot, KSquirrel etc.

•Photo Browsing model has notevolved much.

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Related Work

• Face Detection & Tagging on Social Networking Sites.

• [Zhang et al. MM’03], Automatic annotation of family albums.

• [Davis et al. MM’05], Additional contextual data viz. time of capture, geo-tag, indoor/outdoor scene, co-occurring faces.

Above techniques only improve photo-browsing experience of social engagements.

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Our Goal

• Apart from social engagements, a large chunk of user’s personal photographs consist of tourist places & monuments.

• [Snavely et al. IJCV’08, SIGGRAPH’06] (Photosynth) - CPC Storage, local reconstruction to add new camera’s

• Choudhary et al., Li et al., Sattler et al., Irschara et al. etc. - Localize new query images w/o exhaustive search.

We combine SfM-Reconstruction + Localization to provide intuitive browsing of user photos in 3D space of the monument.

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Assumptions

• Our target platform is an off-the-shelf laptop or a desktop.

• User is expected to click around 5-50 photographs for a particular monument.

• The system should localize these user photographs in areasonable time.

• The system should provide a smooth visualization / transitions of all user photos and ~105 points of the monument.

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System Design(1) Heavy SfM Reconstruction done offline in the cloud

(2) GDBPackage : reconstruction + addnl. information downloaded to local disk

(3) User uploads personal photo’s through a camera / phone

(4) System registers user’sphotos to the point cloud andprovides 3D visualization.

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System Block Diagram

GDBPackage

User Photos

RegistrationModule

VisualizationModule

System is divided in two parts : 1. Registration / Localization Module2. Visualization Module

2 1

EstimatedCamera’s

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Localizing User Photo’s

• Trivial if photograph is taken from GPS enabled deviceand is geo-tagged!

• What if no geo-tag information?

• Two Localization Approaches :Image based search in a geo-tagged Image Dataset[Panda et al.] Geo-locate digital heritage site photos.

Using structure information in SfM Dataset[Irschara et al. CVPR’09], match to nearby similar images.[Li et al. ECCV’10], visibility prioritized 3D-2D matches. [Sattler et al. ICCV’11, ECCV’12], visual words to find 2D-3D matches.

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Localization - Choudhary et al.

• [Choudhary et al. ECCV’12]- Triangulate a seed point in the user photograph.- Further 3D-2D search is guided by visibility probabilities.- Find ~20 independent matches.- Use RANSAC to estimate camera parameters.

Probability Guided 3D-2D correspondence

3D Position

Up Vector

View Direction

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Advantages of Localization Method

• Data for Localization is stored in GDBPackage : (1) Cover Set (2) Visibility Matrix (3) Bi-Partite Visibility Graph

• CPC images need not be stored, data requirements are minimal.

• The method is fast and localizes images at the rate of 1sec/photo.

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Non-Localizable Photographs

• In some cases the images lack sufficient monument geometryfor localization to work :- Occluded by people.- Noisy images of nearby scenery/smaller monuments.- Zoomed in images of smaller monument structures etc.

Zoomed In View of Small Structure

(Pantheon Dataset)

Completely Occludedby People

(Colosseum Dataset)

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Non-Localizable Photographs

• Photographs have time of capture stored in their EXIF-tags.

• A non-localized image is placed at a position that is weightedaverage of its immediate known predecessor and immediateknown successor in time.

• Similarly, linear interpolation is also done for the view-direction vector to get the complete camera pose.

• The above method will not give the exact location, but placing it in temporal neighborhood suffices for display purposes.

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Visualization Module

• 3D Viewer

• Mouse Navigation

• Button Navigation

• Add Screenshot

• Delete Path

• Generate Photo-Tour

• 2D Viewer

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3D Photo Browser : Geometry Directed Photo-Browsing

• Initial Mode : 3D Model and small preview (thumbnails) of

user photographs.

• Select Mode : Animate to clicked photo and detailed view.

• Linear quaternion interpolation of Rotation Matrix for smoothtransitions between images.

• Smooth transitions give a feel of the geometric space of the monument.

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3D Photo Browser : Generating Custom Photo Tours

• User can save the current viewpoint (“Add Screenshots”)

• Once a set of viewpoints are saved, he can smoothly animateover viewpoints. (“Generate Photo-Tour / Animate Path”)

• User can delete the viewpoints and generate a new photo-tour.

• Photo-Tours are a good way to creatively view personalphoto’s taken at a tourist place.

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ResultsMonument # Photos # Registered

PhotosReg. Time

(secs per photo)

Colosseum 24 21 1.01

Colosseum 19 14 0.97

Pantheon 35 22 1.13

Stone Chariot(Hampi)

17 17 1.07

(a) Localization Module

(b) Visualization Module

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Conclusion and Future Work

• Minimal System Requirements.

• Intuitive 3D Visualization of User Photographs.

• Pipeline for 3D personal photo-viewing from SfM reconstruction.

• Port our system to a mobile phone and have a touch/gesture interface.

3D Photo-Viewing & Localization App

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Thank you. Questions?More Results

(a) Hampi Dataset (Stone Chariot)

(b) Pantheon Dataset

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Platform Details

Item Specification

CPU Intel ® CORE ™ i5

Clock Speed 2.44GHZ

RAM 4GB

GPU Intel ® HD Graphics Accelerator