Waveletbased inverse halftoning for error diffused halftones

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Wavelet-based inverse halftoning for error
diffused halftones

• M. Djebbouria, D. Djebourib, and R. Naouma
• AEU - International Journal of Electronics and
  Communications Volume 59, Issue 2, May 30,
  2005, pp. 128-133
• SCI index 120/209 57.4
• Reporter Jen-Bang Feng

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Ootline

• Wavelet Transformation
• Halftone and Inverse Halftone
• The Proposed Scheme
• Experimental Results
• Comments

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Wavelet Transformation (Haar)
ab
a-b
a
b
L
H
a(xy)/2 b(x-y)/2
x and y
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Wavelet Transformation
LL
HL
L
H
LH
HH
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Wavelet Transformation
LL
HL
HL
LH
HH
LH
HH
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(No Transcript)
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Wavelet Transformation
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Halftone and Inverse Halftone
Grayscale
Halftone
Binary
Inverse Halftone
Grayscale
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Error-Diffusion Halftone

• Floyd and Steinberg Kernel

R.W. Floyd and L. Steinberg, An adaptive
algorithm for spatial grayscale, Proc. SID, vol.
17, no. 2 , 1976, pp. 75-77.
Origin
Threshold 128
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Error-Diffusion
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The Proposed Scheme

• Approximate error-diffusion

Halftone Pixel (B or W)
Original Pixel (grayscale)
point spread function
Corrupting noise
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Linear Approximation of Error-Diffusion
4 Kite TD, Evans BL, Bovic AC, Sculley TL.
Digital halftoning as 2-d delta-sigma modulation.
Proceedings of the IEEE International Conference
of Image Processing ICIP97, 1997, pp. 799802.
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Linear Approximation of Error-Diffusion
is the z transform of
Estimate of The Original Pixel
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The Proposed Scheme
Wavelet Transform
Evaluate the dencity
Halftone image
Transformed image
Dencity
Estimate variables
Grayscale image
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Experimental Results
Original Pepper
Halftone Pepper
Recovered Pepper
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Experimental Results
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Comments

• Use other denoising algorithms
• Method to decide edges