Vector Color Error Diffusion Halftoning
Mr. Niranjan Damera-Venkata
Dept. of Electrical and Computer Engineering
The University of Texas at Austin
Friday, November 5th, 4:00 PM, ENS 602
damera-v@ece.utexas.edu
Abstract
Digital halftoning is the process of conversion of continuous-tone
images images (usually 8 bits/pixel) to halftone images (images with N
bits/pixel, N<8). Typically for digital hardcopy applications an 8
bit/pixel image is quantized to 1 bit/pixel.
Error-diffusion is a high-quality technique used to produce digital
halftones. Error-diffusion is a feedback system which attempts to
shape the quantization error into the high-frequency regions, where
its visual impact is much smaller.
I will describe a general framework for the analysis of color
error-diffusion systems. I will account for correlation among the
image planes (usually RGB) explicitly within the model. This model
encompasses previous work in modeling greyscale error-diffusion. We
will validate the model, by using it to predict important well known
effects of error-diffusion such as image sharpening and noise shaping. The
model also leads naturally into an interesting optimization problem
for the design of the filter coefficients, for minimized visual
degradation. Here the filter coefficients are matrices
and not scalar valued. Also conventional convolution is replaced with
matrix-vector multiply accumulates. I will show that a multifilter has
an inherently parallel implementation. We show that we can reorder the
computations such that the parallelism is exposed.
A list of Telecommunications and Signal Processing Seminars is available at
from the ECE department Web pages under "Seminars".
The Web address for the Telecommunications and Signal Processing Seminars is
http://anchovy.ece.utexas.edu/seminars