Color Seamlessness in Multi-Projector Displays Using Constrained Gamut

Morphing

IEEE Visualization, 2009

Behzad SajadiMaxim LazarovAditi Majumder

M. Gopi

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Registration Problem

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Color: Brightness & Chrominance

Brightness: 1D Chrominance (x, y): 2D

3D color gamut

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Color Variation Visualization

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Overview

Prior Art Motivation Algorithm Results

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Prior Art: Overlap Blending

Proj1 Proj2 Proj1 Proj2Overlap Region Overlap Region

Raskar et al SIGGRAPH 1998; Li et al IEEE Computer Graphics and Applications, 2000; Chen et al SPIE Projection Displays, 2001

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Prior Art: Overlap blending

Assumes Uniform brightness in each projector All projectors have similar brightness Projectors are linear devices

Addresses the overlaps only No measurement or correction of intra

or inter projector brightness variation

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BeforeCorrection

OverlapBlending

Prior Art: Overlap Blending

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Prior Art: Measurement with High Resolution Camera

Single ProjectorBrightness Profile

Multi ProjectorBrightness Profile

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Prior Art: Strict Brightness Uniformity

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IEEE TVCG 2003, PROCAMS 2003 Majumder and Stevens

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Prior Art: Strict Brightness Uniformity

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Significant Contrast/ Dynamic Range Compression

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Before

After Strict Brightness Uniformity

Prior Art: Strict Brightness Uniformity

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Prior Art: Constrained Brightness Smoothing

Smoothing is sufficient for perceptual seamlessness Non-linear filtering Maximize dynamic range Solved using dynamic programming

ACM Transactions on Graphics 2005 Majumder and Stevens

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Before

After Strict Brightness Uniformity

Prior Art: Constrained Brightness Smoothing

IEEE TVCG 2003, PROCAMS 2003 Majumder and Stevens

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Before

After Constrained Brightness Smoothing

ACM Transactions on Graphics 2005 Majumder and Stevens

Prior Art: Constrained Brightness Smoothing

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Overview

Prior Art Motivation Algorithm Results

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Motivation: Does it solve the problem?

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Motivation: Our Contribution

Chrominance is constant within projector

Chrominance varies across projectors and in overlaps

Brightness smoothing does not guarantee chrominance smoothing

Constrained chrominance smoothing in addition to brightness smoothing

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3D Gamut Morphing

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Motivation: Key Insight

Smooth transition of chrominance across overlap region Blending of the chromaticity coordinates Only need to manipulate the brightness

proportions of overlapping projectors Manipulate brightness to address

chrominance variation

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Overview

Prior Art Motivation Algorithm Results

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Algorithm: Chrominance profile before registration

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Algorithm: Chrominance Gamut Morphing

ChrominanceGamut Morphing

Horizontal Blending

Vertical Blending

New BrightnessProfiles

Horizontal BlendingAttenuation Map

Vertical BlendingAttenuation Map

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Algorithm: Horizontal Blending

Before Chrominance Blending

After Horizontal Blending

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Algorithm: Vertical Blending

After Horizontal Blending

After Vertical Blending

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Algorithm: Pipeline

Projector BrightnessProfiles

ProjectorChrominance Gamut

Chrominance MorphingAttenuation Map

Chrominance Gamut Morphing

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Algorithm: Chrominance gamut morphing

Modifies brightness profiles Removes C0 brightness discontinuity

Before Correction After Horizontal Blending After Vertical Blending

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Algorithm: Perceptual Brightness Constraining

Does not guarantee imperceptible brightness changes

Apply Majumder et. al. 2005 to constrain the brightness variations

Retains chrominance gamut morphing

After Vertical BlendingAfter Brightness Constraining

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Algorithm: Bezier-based Brightness Smoothing

Brightness profile is not derivative continuous after Majumder et. Al. 2005

Assures Cn intensity continuity Retains chrominance gamut morphing

After Vertical BlendingAfter Brightness ConstrainingAfter Bezier-based Smoothing

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Algorithm: Brightness Smoothing

BrightnessSmoothing

PerceptualBrightness Constraining

Vertical Bezier-basedBrightness Smoothing

New BrightnessProfiles

Brightness SmoothingAttenuation Map

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Algorithm: Offline Correction Pipeline

Chrominance Gamut Morphing

Projector BrightnessProfiles

ReconstructChrominance Gamut

New BrightnessProfiles

Brightness Smoothing

Final AlphaMask (A)

White BalancingPrior to Correction

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Color Variation Visualization

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Algorithm: Online Image Correction

Apply Alpha Mask

Apply Projector Transfer Function

InputImage

Custom Linearization Function

Linearize Input Image

Final AlphaMask (A)

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Overview

Prior Art Motivation Algorithm Results

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Results: More General Pictures

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Results: Extends to any Geometry

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BeforeCorrection

OverlapBlending

Final Result

Majumderand Stevens

2005

Results: Comparison

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Conclusion

First method that Complete 3D color registration

Addresses spatial variations in both chrominance and brightness

High quality display with commodity projectors

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Future Work

Extend to non-developable surfaces Address intra-projector color

variations

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Questions?

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Prior Art: Color Seamlessness

Brightness Chrominance

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