Painterly Rendering of Image

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Painterly Rendering of Image

• Ningning Zhu
• May 16, 2001

2
Introduction

• Art and illustration have historically been the
  sole domain of artists.
• Easy creation of highly realistic images
• Less advanced of non-photorealistic work

3
Design Issues

• How big is the brush size?
• Color of a stroke?
• Where to start stroke?
• Where the stroke goes?
• Where the stroke stops?
• How to draw the stroke?
• How to adjust the painting style?

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How big is the brush size?

• Multiple brush size
• (style parameter)
• Layered painting
• Blur original image
• Cubic filter
• filter stretch (style parameter)
• Problem(image becomes darker)

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Color of stroke

• Remain constant within one stroke
• Color Jitter from original image
• (style parameter)

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Where to start the stroke

• Divide the original image in to grid
• Grid Size (style parameter)
• Area Error
• Thresh hold (style parameter)
• Canvas Initialization
• Start from largest error point

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Where the stroke goes?

• Control points
• Normal of gradient direction
• Chose one of the two normal
• Curvature factor
• (style parameter)

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Where the stroke stops?

• Min stroke length assured
• Edge encountered
• Gradient is near zero
• Max stroke length reached
• Better without this stroke
• Current Canvas color
• Stroke color
• Reference image color

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How to draw the stroke?

• Layer by Layer
• Random order of stroke within layer
• Draw each control point as a circle
• Add more points for long stroke
• More than 4 control points
• Using spline curve

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How to adjust painting style

• Using style parameter
• Brush size (min, max, multiple layer)
• Filter stretch
• Curvature parameter
• Grid size
• Area error thresh hold
• Color jitter

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Result (1)

• Original Painterly rendering

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Result (2)

• Original
• Painted