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Shape-Preserving Half-Projective Warps for Image Stitching. Che-Han Chang 1 , Yoichi Sato 2 , Yung-Yu Chuang 1 1 National Taiwan University 2 The University of Tokyo. Image stitching. Geometric transformation. Projective transformation (Homography). Projective warp. Image compositing. - PowerPoint PPT Presentation
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Che-Han Chang1, Yoichi Sato2, Yung-Yu Chuang1
1National Taiwan University 2The University of Tokyo
Shape-Preserving Half-Projective Warps for Image Stitching
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Image stitching
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Geometric transformation
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Projective transformation(Homography)
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Projective warp
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Imagecompositing
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• Misalignment (overlapping regions)• Geometric distortion (non-overlapping regions)– Stretched shapes shape distortion– Non-uniform scaling area distortion
Projective Warp
Misalignment
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• Misalignment (overlapping regions)• Geometric distortion (non-overlapping regions)– Stretched shapes shape distortion– Non-uniform scaling area distortion
Projective Warp
Distortion
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As-Projective-As-Possible Warp
Projective Warp
Locally aligned
Distortion
Globally aligned
Distortion
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Key idea: Replacing it bya similarity transformation.
As-Projective-As-Possible Warp
(scaling, rotation, translation)
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Source
Projective warpSimilarity warp Our warp
We propose shape-preserving half-projective warp, a spatial combination of a projective transformation and a similarity transformation.
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Projective warp Our warp
APAP warp APAP + Our warp
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GoalGiven a projective transformation, construct a warp that gradually changes from projective to similarity.
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Linear mapping
H
Scaleup Scale
down
Construction
+
Analysis
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Change of coordinates
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H
Scaleup Scale
down
As , area distortion
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H
H becomes linear if u is a constant
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similarity transformation
H
H becomes linear if u is a constant
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H
S
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H
S
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C0 continuity C1 continuity
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Given H, l1 and l2, determine S and T such that the resulting warp is C1 continuous.
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C1C1
Given H, l1 and l2, determine S and T such that the resulting warp is C1 continuous.
C1 continuity on l1 Boundary constraints
C1 continuity on l2
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Given H, l1 and l2, determine S and T such that the resulting warp is C1 continuous.
C1 continuity on l1 Boundary constraints
C1 continuity on l2
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Given H, l1 and l2, determine S and T such that the resulting warp is C1 continuous.
C1 continuity on l1 Boundary constraints
C1 continuity on l2
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Two-view stitching
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Two-view stitching
Projective warp
Our warp
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Given H, l1 and l2, determine S and T such that the total warp is C1 continuous.
Parameters
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Optimizing parametersWe want that each image undergoes a similarity transformation as much as possible.
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Multiple image stitching
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Projective Refinedwarp
Refinedwarp
APAP
Combined warp
Our warp
Combining with the APAP warp
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OriginalAutoStitch
Our warpProjective warp
Results
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AutoStitch
Projective warp
Our warp
Results
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• A novel parametric warp for image stitching• Parameter selection could be improved
Conclusion
Projective warpSimilarity warp Our warp
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Thank you!Any questions?
