Halftoning with Thresholding
Heri Prasetyo, S.Kom., M.Sc.Eng., Ph.D.
Department of Informatics Universitas Sebelas Maret (UNS)
Surakarta, Indonesia
Multimedia System
Outline…
Outline…
• Introduction to Halftoning
• Halftoning with Image Thresholding
– General Thresholding Scheme – Additive Noise
• Experimental Results
Introduction to Halftoning Introduction to Halftoning
• Halftoning is a method for creating the illusion o f continuoustone output with a binary device.
• Many image rendering technologies only have binary output.
– For example, printers can either “fire a dot” or not.
• Effective digital halftoning can substantially imp rove the quality of rendered images at minimal cos t.
Halftoning with Image Thresholding Halftoning with Image Thresholding
• Assume that the image falls in the range of 0 to 2 55.
• Apply a space varying threshold, .
• Where and are the halftone pixel and input image , respectively at position .
• will generally be in units of absorptance.
•
Constant Threshold Constant Threshold
• Suppose that an image is in the range .
• The value 255 denotes black pixel, where 0 represe nts white.
• The minimum squared error quantizer is a simple th reshold:
• where T = 127.
• This produces a poor quality rendering of a contin uous tone image.
•
Constant Threshold with Additive Noise Constant Threshold with Additive Noise
• Each pixel in input image is injected with additiv e noise.
• The noise can be generated using specific random n umber generator:
– Uniform Random Number: . – Gaussian Random Number: .
• The thresholding can be performed as follow:
• The value is constant.
•
Halftoning with Image Thresholdi ng
Halftoning with Image Thresholdi ng
Input Image
Input Image Image AImage A
Image B
Image B Image CImage C
Threshold Image A:
Thresholded Image Image B:
Thresholded Image after Uniform Noise Additive with
Image C:
Thresholded Image after Gaussian Noise Additive with
Halftoning with Image Thresholdi ng
Halftoning with Image Thresholdi ng
Input Image
Input Image Image AImage A
Image B
Image B Image CImage C
Threshold Image A:
Thresholded Image Image B:
Thresholded Image after Uniform Noise Additive with
Image C:
Thresholded Image after Gaussian Noise
Halftoning with Image Thresholdi ng
Halftoning with Image Thresholdi ng
Input Image
Input Image Image AImage A
Image B
Image B Image CImage C
Threshold Image A:
Thresholded Image Image B:
Thresholded Image after Uniform Noise Additive with
Image C:
Thresholded Image after Gaussian Noise Additive with
Halftoning with Image Thresholdi ng
Halftoning with Image Thresholdi ng
Input Image
Input Image Image AImage A
Image B
Image B Image CImage C
Threshold Image A:
Thresholded Image Image B:
Thresholded Image after Uniform Noise Additive with
Image C:
Thresholded Image after Gaussian Noise
Effect of Different Thresholding Paramet er
Effect of Different Thresholding Paramet er
• The threshold values and induce the thresholding performance.
• The thresholding results are investigated under fi x value of with various values.
• The halftoning performance is examined under visua l investigation.
•
Halftoning with Image Thresholdi ng
Halftoning with Image Thresholdi ng
Input Image
Input Image Image AImage A
Image B
Image B Image CImage C
Threshold Image A:
Thresholded Image Image B:
Thresholded Image after Uniform Noise Additive with
Image C:
Thresholded Image after Gaussian Noise
Halftoning with Image Thresholdi ng
Halftoning with Image Thresholdi ng
Input Image
Input Image Image AImage A
Image B
Image B Image CImage C
Threshold Image A:
Thresholded Image Image B:
Thresholded Image after Uniform Noise Additive with
Image C:
Thresholded Image after Gaussian Noise Additive with
Halftoning with Image Thresholdi ng
Halftoning with Image Thresholdi ng
Input Image
Input Image Image AImage A
Image B
Image B Image CImage C
Threshold Image A:
Thresholded Image Image B:
Thresholded Image after Uniform Noise Additive with
Image C:
Thresholded Image after Gaussian Noise
Halftoning with Image Thresholdi ng
Halftoning with Image Thresholdi ng
Input Image
Input Image Image AImage A
Image B
Image B Image CImage C
Threshold Image A:
Thresholded Image Image B:
Thresholded Image after Uniform Noise Additive with
Image C:
Thresholded Image after Gaussian Noise Additive with
Effect of Different Thresholding Paramet er
Effect of Different Thresholding Paramet er
• The thresholding results are investigated under fi x value of with various values.
• The halftoning performance is examined under visua l investigation.
• Different values of yield different results.
•
Halftoning with Image Thresholdi ng
Halftoning with Image Thresholdi ng
Input Image
Input Image Image AImage A
Image B
Image B Image CImage C
Image A:
Thresholded Image with
Image B:
Thresholded Image with
Image C:
Thresholded Image with
Halftoning with Image Thresholdi ng
Halftoning with Image Thresholdi ng
Input Image
Input Image Image AImage A
Image B Image B
Additive Uniformly Noise
Image A:
Thresholded Image with
Image B:
Thresholded Image with
Image C:
Thresholded Image
Image C Image C
Halftoning with Image Thresholdi ng
Halftoning with Image Thresholdi ng
Input Image
Input Image Image AImage A
Image B Image B
Additive Gaussian Noise
Image A:
Thresholded Image with
Image B:
Thresholded Image with
Image C:
Thresholded Image with
Image C Image C
