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Paint By Numbers : Abstract Image Representation Paul Haeberli Silicon Graphics Computer Systems ACM SIGGRAPH Computer graphics Proceeding of 17 th , 1990 Outline Motivation Overview Painting Techniques Stroke Attributes Operations on Paintings Advanced Techniques Spice for Images

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paint by numbers abstract image representation

Paint By Numbers : Abstract Image Representation

Paul Haeberli

Silicon Graphics Computer Systems

ACM SIGGRAPH Computer graphics

Proceeding of 17th, 1990

outline
Outline
  • Motivation
  • Overview
  • Painting Techniques
  • Stroke Attributes
  • Operations on Paintings
  • Advanced Techniques
  • Spice for Images
  • Conclusion
  • Further work
motivation4
Motivation
  • Producing images indistinguishable from photograph
  • Graphic designer’s choice
    • Photorealistic, Not always the best choice
    • “How much use is a photograph to mechanics when they already have the real thing on front of them?”[Lansdown and Schofield]
    • Visual effect intended by designer

[Lansdown and Schofield] J.Lansdown and S.Schofield. Expressive rendering: A review of nonphotorealistic techniques. IEEE ComputerGraphics and Applications, 1995.

overview6
Overview
  • Alternative to photorealism
  • Painterly rendering
  • Creation of artistic, stylized and abstract images
    • Impressionistic painting
  • Brush stroke control
  • User interactive system
operation
Operation
  • Information from source image
    • Cursor across the canvas
    • Sampling color from image
  • Paint a brush stroke
    • Location
    • Color
    • Size
    • Direction
    • Shape
stroke location
Stroke Location
  • Stochastic distribution around cursor
  • Example of interactive particle system[Reeves]

[Reeves] William T. Reeves and Ricki Blau, “Approximate and probabilistic algorithm for shading and rendering structured particle systems”, Computer Graphics, 1985.

stroke color
Stroke Color
  • RGB and alpha value
  • Time limitation to pick new color
    • “put-that-color-there” procedure[Lewis]
    • Restrict to small number of color

[Lewis] John-Peter Lewis, “Texture Synthesis for Digital Painting”, Computer Graphics, 1984.

stroke size and orientation
Stroke Size and Orientation
  • Size
    • Control by cursor speed
      • Easy to create rough representation
    • Control by arrow keys
  • Orientation
    • Direction of cursor
    • Mouse gesture
    • Image gradient
stroke shape
Stroke Shape
  • Shape
    • Significant influenceto final painting
    • Circle, rectangle, line,scattering of points,polygon, cone, user-defined shape
painting example14
Painting Example

Diagonal stroke

Pointillist representation

painting example15
Painting Example
  • • Cone shape brush
    • • Voronoi diagram polygon resterizing hardware• rendering of cones to construct 2D Voronoi diagrams of points

Cone shape

painting description
Painting Description
  • Painting as an ordered set of strokes
  • Containing stroke information
  • Operations on paintings
    • Transform painting into RGB images
    • Unary operation – scaling, sorting, adding noise, etc.
    • Binary operation – interpolation, extrapolation, animation, etc
brush direction
Brush Direction
  • Brush direction using second image
edge drawing
Edge drawing
  • Edge drawing using luminance gradient
texture mapping
Texture mapping
  • Brush texture mapping
sampling geometry
Sampling Geometry
  • Sampling geometry using Ray-tracing
approximation
Approximation
  • Approximation using Relaxation
edge enhancement
Edge enhancement
  • “Pushing edge”
  • More explicit depth relationship
  • Using unsharp masking
color enhancement
Color enhancement
  • Increase saturation
  • Lum = 0.3*R + 0.59*G + 0.11*B
  • Extrapolation
color restriction and background color
Color restriction and Background Color
  • Color restriction
    • Limited color for overall harmony and unity
    • Color quantization of source image
    • Noise for no contouring
  • Background cover
    • Unity and integrity
    • Color perception
conclusion
Conclusion
  • A system for producing abstract image
    • The first experiment on NPR
    • Making stylized abstract image
    • Interactive processing
    • Motivations for future works
      • Media
      • Method
inspiration
Inspiration
  • Haeberli’s work
    • The first work on NPR
    • Some issues
      • Stroke methods, attributes, animation, etc
  • After Haeberli’s work
    • Considerable works on painting system
    • Two large categorization
      • Digital analogues
      • Automatic stroke
digital analogues
Digital analogues
  • Salisbury et al. 1994
    • Pen and ink
  • Curtis et al. 1997
    • Watercolor
  • Sousa et al. 1999
    • Pencil drawing
automatic stroke
Automatic stroke
  • Litwinowicz, 1997
  • Hertzmann, 1998
  • Shiraishi and Yamaguchi, 2000
  • Only global effect by user
    • Brush size or shape
stroke dimension
Stroke Dimension
  • Dana, 1996
    • 8D dimension for social visualization[Dana]
    • To show social data

Animation

  • Meier, 1996
    • Using particle rendering methods