Automatic Joiners - Carnegie Mellon University
Transcript of Automatic Joiners - Carnegie Mellon University
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Automatic Joiners
Ekapol Chuangsuwanich
15-463 Computational PhotographyFall 2007
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Stitching ImagesPanoramas
Uses images taken from a single view pointWhat if the images are taken from different view points?What if the images are taken from different view points?
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Multi-views
Pictures taken 5 steps apart.
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Multi-views
??
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JoinersDavid HockneyLayered of photographs taken from multiple viewpoints
http://en.wikipedia.org/wiki/David_Hockney
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Joiners
Takes around an hour to do manual alignment.
http://www.flickr.com/photos/qtr/27676970
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Automatic JoinersAutomatic JoinersSolution to the lazy artists
Zelnik-Manor and Perona, “Automating joiners”
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Overall FrameworkFind correspondencesFind global alignment between imagesFind the best ordering of the imagesReadjustmentReadjustment
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1. Feature CorrespondenceUse Scale-Invariant Feature Transform (SIFT) to extract features from the image
lpoolUse RANSAC to eliminate outliers
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2. Find Global AlignmentUse similarity transform to align the images.Similarity transform is a combination of scale (c), rotation (R), and transition (t)
Y = cRX + twhere X and Y are the sets of matched features
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Global alignmentsInput
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3. ReorderFind the order of the images such that the gradient across the boundaries are
i i i dminimized.
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Before Reorderingg
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After Orderingg
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Some observationsPoints that are hidden behind other images are not as importantare not as important as the one that can be seen.Points closer to the borders are more important.
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4. ReadjustmentRealign the images
di taccording to the ordering i f tiinformation.Use 10 points closest to the border.
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Before Realignmentg
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After Realignmentg
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Wean
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Align
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Order
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Realign
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Walking to the Sky
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Everyone’s favorite coke machine
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ReferencesZ l ik M Lihi d P Pi t “A t ti J i ”Zelnik-Manor, Lihi and Perona, Pietro. “Automating Joiners.” http://www.vision.caltech.edu/lihi/Demos/AutoJoiners.htmlUmeyama, Shinji. “Least-Squares Estimation of Transformation Parameters Bet een T o Point Patterns ”Transformation Parameters Between Two Point Patterns.” IEEE Transactions on Pattern Analysis and Machine Intelligence. Vol. 13. No 4. April 1991Brown M “Recognising Panoramas ”Brown, M. “Recognising Panoramas.” http://research.microsoft.com/~brown/papers/iccv2003.pdfLowe, David. “SIFT Keypoint Detector.” http://www cs ubc ca/ lowe/keypoints/http://www.cs.ubc.ca/~lowe/keypoints/
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The EndThe EndThe EndThe End
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Questions?Q