ObjectBased Image Editing, William A. Barrett and Alan S. Cheney, SIGGRAPH 2002

1
Object-Based Image Editing,William A. Barrett
and Alan S. Cheney, SIGGRAPH 2002

• Summary talk by Lex Stein for CS278
• 04/14/2004

2
Image-editing methods

• Pixel-based push pixels around.
• Region-of-interest (ROI) global manipulation of
  axis-aligned bounding box.
• Image-based affect the entire image like a
  rubber sheet.

3
The Problem

• Image editors want something between pixel and
  global manipulation that operates on the objects
  within images.
• Challenges operating at interactive rates,
  hole-filling, preserving texture, aliasing,
  non-linear transforms.
• Tricks indirect editing, texture spraying.

4
Tobogganed Regions of Accumulated Plateaus (TRAPs)

• Image is automatically segmented into TRAPs using
  gradient methods.
• TRAPs are the primitives that provide texture for
  hole-filling and texture spraying.
• TRAPs are not objects. Users manually create
  objects from TRAPs.
• An objects TRAPs are triangulated to improve
  object transform efficiency.

5
Creating triangulated objects
1. TRAP segmentation
2. Manual aggregation of TRAPS into an object
3. Triangulation
6
Object-Based Editing Operations

• Suite includes linear transforms that update at
  interactive rates.
• New nonlinear per-object operators stretching,
  warping, and rotational bend.
• Object transforms are computed in their own layer
  and in a local coordinate system for speed.
• Objects are antialiased with their background.
• Objects have adjustable transform pivot points.

7
Background Filling

• Two methods implemented
• Scale-down (2a-3a)
• Random-grid (2b-3b)
• Both use TRAPs for regions of texture.
• The entire space behind an object is filled in
  whenever the object is modified.

8
Texture-Preserving Operations

• Instead of stretching TRAPs, keep their size
  fixed and copy them to fill a warped region.

original
cutoff map
stretched
stretched more
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Non-linear Transformations

• Ai is a general attenuation multiplier.
• stretch
• rotation
• stretches and rotations are computed in two steps
  but require only a single user interaction.

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Curve Deformers

• The user specifies the Ais (can edit the
  points with automatic function interpolation).
  Consider this to be a feature. Different Ais
  will yield different transforms.

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Papers Results and Conclusion

• Speed and quality
• Faster and better-looking than the competition on
  the benchmarks.
• Claim
• OBIE changes fundamentally the way image editing
  is performed by changing the granularity of
  operations.
• Improvements
• more sophisticated curve deformers.
• Challenges
• when gradients disappear at object boundaries
• texture with regular structure.

12
Issues

• Specifying the attenuation multipliers (Ais).
  Need different multipliers for different kinds of
  objects. What about objects with complicated
  internal structure and mechanics?
• Manual aggregation of TRAPs into objects.
  Consider Figure 2(a).