@phdthesis{Veryovka:1999:TCD,
optnote = {},
author = {Oleg Veryovka},
optkey = {},
optannote = {},
opttype = {},
url = {http://wwwlib.umi.com/dissertations/fullcit/NQ46940},
localfile = {papers/Veryovka.1999.TCD.pdf},
address = {Canada},
school = {Department of Computing Science, University of Alberta},
optmonth = {},
doi = {http://doi.acm.org/10.1145/931439},
optabstract = {},
optstatus = {},
abstract = {There are two ways to represent visual information: photographic
and artistic. Photographic approaches attempt to approximate an
image despite the limitations of the output medium. Traditional
halftoning takes a photorealistic approach. In an artistic
rendering visual information is interpreted by the artist and
displayed accordingly using the chosen medium. The
non-photorealistic rendering area of computer graphics develops
tools and techniques to enable interpretive rendering in digital
media. Texture is an inevitable artifact of halftoning. The
challenge of photorealistic halftoning is to preserve image
features --- tone, edges, and textures --- and to hide the
halftoning texture. To the contrary, in artistic rendering texture
is often used as a visual cue and an expressive mean. In this
thesis 1 explore the use of halftoning texture to enhance the
representation of visual information in both photorealistic and
interpretive rendering applications. However, this use of texture
requires methods and techniques to control texture in halftoned
images. Thus, the objective of this work is to control the
appearance of texture in the resulting images. My technique of
texture control is based on previous halftoning algorithms:
ordered dither and error diffusion. I use the ability of the
ordered dither algorithm to define halftoning texture through the
arrangement of threshold values in its dither matrix. The thesis
describes two methods of generating dither matrices: image
processing and procedural texturing. The use of texture based
dither matrices guarantees the appearance of desired textures in
the halftoned image. The strength of the resulting texture is
controlled by combining ordered dithering with the error diffusion
process. The ability to define and control texture in the
halftoned image leads to the use of this texture as an expressive
mean in image rendering. A user may introduce a variety of
artistic effects into the image. Examples include embossing an
image with a texture or text; approximation of traditional art
styles and rendering techniques - pencil drawing, carving, oil
brush painting. The thesis also includes techniques that allow us
to map texture features to enhance representation of image
gradient. 3-D scene information and subjective user defined
information. This study is a contribution to both photorealistic
and artistic halftoning of images. It is a new approach to
non-photorealistic rendering. Unlike previous techniques,
interpretive halftoning is not limited to any particular style of
rendering. Moreover, artistic effects generated by previous
techniques may be approximated. Investigation of texture control
in halftoning extends photorealistic dithering techniques. It
turns out that the use of image based dither matrix improves
rendering of the original image textures and edges. Also, the
thesis includes investigation of an image quaiity measure that
allows us to analyze halftoned images. This measure is based on
multi-scale analysis of image edges and thus enables us to
quantify edge distortions introduced by the halftoning
algorithm.},
title = {{T}exture {C}ontrol in {D}igital {H}alftoning},
year = {1999},
}
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