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Artistic screening is a new image reproduction technique incorporating freely created artistic screen elements for generating halftones. Fixed predefined dot contours associated with given intensity levels determine the screen dot shape's growing behavior. Screen dot contours associated with each intensity level are obtained by interpolation between the fixed predefined dot contours. A user-defined mapping transforms screen elements from screen element definition space to screen element rendition space. This mapping can be tuned to produce various effects such as dilatations, contractions and nonlinear deformations of the screen element grid. Discrete screen elements associated with all desired intensity levels are obtained by rasterizing the interpolated screen dot shapes in the screen element rendition space. Since both the image to be reproduced and the screen shapes can be designed independently, the design freedom offered to artists is very great. The interaction between the image to be produced and the screen shapes enables the creation of graphic designs of high artistic quality. Artistic screening is particularly well suited for the reproduction of images on large posters. When looked at from a short distance, the poster's screening layer may deliver its own message. Furthermore, thanks to artistic screening, both full-size and microscopic letters can be incorporated into the image reproduction process. In order to avoid counterfeiting, banknotes may comprise grayscale images with intensity levels produced by microletters of varying size and shape
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Artistic Screening
Victor Ostromoukhov, Roger D. Hersch
Ecole Polytechnique Fédérale de Lausanne(EPFL), Switzerland
Artistic screening is a new image reproduction technique incorpo-
ratingfreelycreatedartistic screenelements forgenerating halftones.
Fixed predefined dot contours associated with given intensity lev-
els determine the screen dot shape's growing behavior. Screen dot
contours associated with each intensity level are obtained by inter-
polation between the fixed predefined dot contours. A user-defined
mapping transforms screen elements from screen element definition
space to screen element rendition space. This mapping can be tuned
to produce various effects such as dilatations, contractions and non-
linear deformations of the screen element grid. Discrete screen
elements associated with all desired intensity levels are obtained by
rasterizing the interpolated screen dot shapes in the screen element
rendition space. Since both the image to be reproduced and the
screen shapes can be designed independently, the design freedom
offered to artists is very great. The interaction between the image to
be reproduced and the screen shapes enables the creation of graphic
designs of high artistic quality. Artistic screening is particularly
well suited for the reproduction of images on large posters. When
looked at from a short distance, the poster's screening layer may
deliver its own message. Furthermore, thanks to artistic screen-
ing, both full size and microscopic letters can be incorporated into
the image reproduction process. In order to avoid counterfeiting,
banknotes may comprise grayscale images with intensity levels
produced by microletters of varying size and shape.
Image reproduction, graphic design, halftoning, artistic screening,
1 Introduction
Halftoning and screening techniques are aimed at giving the impres-
sion of variable intensity levels by varying the respective surfaces
of white and black within a small area. Traditional techniques use
repetitive screen elements, which pave the plane and within which
screen dot surfaces define either white or black parts [17]. As long
as the screen element period is small, or equivalently, the screen
EPFL/LSP CH-1015 Lausanne, Switzerland,
Proceedings of SIGGRAPH'95,
In ACM Computer Graphics, Annual Conference Series, 1995, pp. 219-228.
Figure 1: Escher's Sky and Water woodcut (reproduced with per-
mission, ©1995 M.C. Escher, Cordon Art, Baarn, Holland).
frequency is high (for example 150 screen elements per inch), dis-
tinct screen elements cannot be perceived by the human eye from a
normal viewing distance [11]. However, in order to achieve such
high screen frequencies, resolutions above 2400 dpi are required.
With office printers, respectively photocomposers, having resolu-
tions between 240 and 800 dpi, respectively between 1200 and 2400
dpi, halftoning or screening effects cannot be completely hidden.
This explains why so much effort has been invested in develop-
ing halftoning techniques which reduce the impact of halftoning
artifacts as much as possible [7].
Wewould like to take a different approach. Instead of looking at
the halftoning layer as a pure functional layer producing undesired
artifacts, we propose a new screening technique which enables the
shape of screen dots to be tuned. By creating artistic screens which
may take any desired shape, screening effects, which up to now
were considered to be undesirable, are tuned to convey additional
information for artistic purposes.
The approach we follow is somewhat related to the pen and
ink illustration techniques where pen strokes are used for sketching
illustrations, at the same time creating texture and intensities. While
computer-aidedpen andinkillustration systems[18] aim tooffer the
same flexibility astraditional pen-based stroking, artisticscreening,
as presented in this contribution, is a new computer-based image
reproduction technique, which opens a new design space for artistic
For artistic screening, we extend the dynamics of screen dot
SIGGRAPH'95 Computer Graphics Proceedings, Annual Conference Series, 1995
Figure2: Mosaic tilework faces walls surrounding the courtyard of
the Attarine Medeza, Fez (Courtesy of R. and S. Michaud, Rapho).
shapes by using more sophisticated artistic shapes as screen dots.
We would like to have full control over the evolution of the artistic
screen dot shape and at the same time offer a halftoning method
which is competitive with regard to conventional high-resolution
clustered-dot screening. We have sought our inspiration in the
work of medieval artists [1], who after having tiled the plane with
repetitive polygonal patterns, created beautiful ornaments in each
of the separate tiles (Fig. 2). Escher [12] further developed this
technique by letting shapes circumscribed by a regular tile smoothly
grow into one another (Fig. 1). The present work is also related
to the decorative motives found in Islamic art which incorporate
beautiful calligraphic work with letter shapes well-distributed over
a given geometric surface (Fig. 3).
Previous attempts to develop screen dots having non-standard
shapes were aimed at improving the tone reproduction behavior at
mid-tones [9]. Elliptic screen dots for example, have an improved
tone reproduction behavior due to the fact that at the transition
between 45% and55% intensity, at firstonly two neighbouring dots
touch each other and only after a certain increase of intensity does
the screen dot touch all its four neighbours (Fig.4).
State of the art techniques for generating screen dot shapes are
based on dither threshold arrays which determine the dot growing
behavior. Since the dither threshold levels associated with the
dither cells of a dither threshold array specify at which intensity the
corresponding binary screen element pixels are to be turned on, the
so generated screen dot shapes have the property of overlapping
one another.
In order to generate screen dots of any shape, which need not
overlap one another and which may have self-intersecting contours,
we propose a new way of synthesizing screen dot shapes. We define
the evolution of screen dot contours over the entire intensity range
by interpolating over a set of predefined fixed dot contours which
define the screen dot shape at a set of fixed intensity levels. Once
the evolving shape of the halftone dot boundary is defined exactly
for every discrete intensity level, the screen elements associated
with each intensity level are rasterized by filling their associated
screen dot contours (Section 3).
After having generated the screen elements, digital screening
proceeds with the halftoning process described in more detail in
Section 2. This halftoning process distinguishes itself from previ-
ous halftoning methods described in the literature [7] by the fact
that the screen elements associated with every intensity level are
precomputed and that no comparisons between original gray levels
and dither threshold levels are necessary at image generation time.
Furthermore, it ensures smooth transitions of the artistic halftone
pattern in regions of high intensity gradients by applying bi-linear
Figure3: Thoulthi classicalcalligraphyby MajedAl Zouhdi (Cour-
tesy of H. Massoudy, [8]).
interpolation between source image pixels.
The results obtained with artistic screening (Section 5) demon-
strate that contour-based generation of halftone screens effectively
provides a new layer of information. We show how this layer of
information can be used to convey artistic and cultural elements
related to the content of the reproduced images. Since there is no
limitation to the size of the halftone screen elements, they can be
made as large as the image itself. The introduced mapping (Sec-
tion 4) between screen element definition space and screen element
rendition space enables the production of highly desirable, smooth
deformations of screen dots, without affecting the image content. In
addition totheir nicevisual properties, geometrictransformations of
screen element shapes are of high interest for creating microscopic
letters for security purposes, for example on banknotes.
Since artistic screening relies on the evolution of dot shapes at
continuous intensity levels and since it allows building large screens
(superscreens) containing arrays of screen subshapes, it is also able
to produce traditional halftone screen dots having those frequencies
and orientations which are required for traditional colour reproduc-
tion. Artistic screening may therefore also be used at high resolu-
tion as an alternative to current exact-angle clustered-dot screening
techniques [2].
2 The halftoning process
Classical clustered-dot halftoning techniques rely on ordered dither
threshold arrays. A dither threshold array is conceived as a discrete
tile paving the output pixel plane. A dither threshold level is asso-
ciated with each elementary cell of the dither threshold array. The
succession of dither threshold levels specifies the dot shape growing
Figure 4: Traditional screen dot shapes, above with round and
below with elliptic screen dots, produced by the artistic screening
software package.
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0420 27 31 18 10 3
11 15 36 44 40 35 14 7
19 32 48 52 56 51 39 23
28 41 57 61 60 55 47 26
24 45 53 62 63 59 43 30
21 37 49 58 54 50 34 17
512 33 42 46 38 13 9
1816 29 25 22 62
0420 27 31 18 10 3
11 15 36 44 40 35 14 7
19 32 48 52 56 51 39 23
28 41 57 61 60 55 47 26
24 45 53 62 63 59 43 30
21 37 49 58 54 50 34 17
512 33 42 46 38 13 9
1816 29 25 22 62
64 40
(a) (b) (c)
Figure 5: Spot function, dither matrix, and corresponding screen dot shapes.
Two fixed predefined contours Interpolated contours Discretized screen element
Figure 6: Artistic screening with a screen dot pattern inspired by Escher reproduced on an image representing a grayscale wedge.
behavior at increasing intensity levels (see Fig. 5). Dither thresh-
old levels can either be specified manually or algorithmically [17].
Previous algorithmic approaches for generating discrete dither ar-
input image pixel boundaries
input image pixel boundaries
Figure 7: Effect of rapid intensity transitions on (a) standard
clustered-dot screen elements and (b) artistic screen elements (en-
rays are based on spot functions [2]. A spot function z = S(x, y)
defines the dither threshold levels for a dither element tile defined
in a normalized coordinate space (-1 x, y < 1).
input image pixel boundaries
input image pixel boundaries
Figure 8: Rapid intensity transitions smoothed out by bi-linear
interpolation of source image pixels at halftoning time on (a) stan-
dard clustered-dot screen elements and (b) artistic screen elements
S(x, y) < z
SIGGRAPH'95 Computer Graphics Proceedings, Annual Conference Series, 1995
a) fixed predefined contours
b) scaled fixed predefined contours
d) interpolation parameters
= 0% = 25% = 50% = 75%
= 100%
0% 25% 50% 75% 100%
0% 25% 50% 75% 100%
8.3% 16.7% 33.3% 41.7% 58.3% 66.7% 83.3% 91.7%
Figure 9: Simple dot shape obtained by blending between a set of fixed contours.
By discretizing this spot function, i.e, by computing its eleva-
tion at the coordinates of the centers of individual screen cells, and
by numbering successive intersection points according to their ele-
vations (Fig. 5b), one obtains the dither threshold array used for the
halftoning process. The comparisons between given source image
pixel intensity levels
and dither threshold levels determine the
surface of a screen dot. For example, the dot shape associated with
an input intensitylevel of 40/ 64 is obtainedby activating all screen
element pixels with threshold values 40 or greater (Fig. 5c).
With a given dither threshold array, the classical halftoning
process consists of scanning the output bitmap, for each output
pixel, finding its corresponding locations both in the dither array
and in the grayscale input image, comparing corresponding input
image pixel intensity values to dither array threshold levels and
accordingly writing pixels of one of two possible ouput intensity
levels to the output image bitmap.
Since artistic screening is not based on dither matrices, we pre-
compute the screen elements (halftone patterns) representing each
of the considered intensity levels. The halftoning process associ-
ated with artistic screening consists of scanning the output bitmap,
and foreach binary output pixel, findingits corresponding locations
both in the grayscale input image and in the screen element tile. The
input image intensity value determines which of the precomputed
screen elements is to be accessed in order to copy its bit value into
the current output bitmap location (Fig. 6a). This process may be
accelerated by executing the same operations with several binary
output pixels at a time [10].
In standard clustered-dot screening, due to the comparison be-
tween source pixel intensity values and dither threshold values,
rapid transitions within a single halftone screen element are pos-
sible (Fig. 7a). They ensure that rapid intensity transitions occur-
ring in the original image are preserved in the halftoned image.
With artistic screen elements however, rapid transitions may in-
troduce unacceptable distortions in the screen dot shape (Fig. 7b).
Smoother transitions are obtained by computing for each output
bitmap pixel the corresponding interpolated gray intensity value at
the corresponding location in the source image pixmap (bi-linear in-
terpolation). Smoother intensity variations will be associated with
output bitmap neighbourhoods, which will in turn smooth out the
transitions within single artistic screen elements (Fig. 8). If the
original image is scanned at high resolution (300 dpi and higher),
undesired sharp intensity transitions may be avoided by applying
to it a low-pass filter. There is a trade-off between the continuity
of the halftone dot shapes and the faithful reproduction of sharp
3 Contour-based generation of discrete screen el-
Spot functions
S(x, y)
generating simple screen dot shapes can be
described easily. More complicated spot functions for generating
shapes such as the dot shapes described in Fig. 6 are impossible to
generate, since they cannot be described as single valued functions.
In order to generate complicated dot shapes capable of repre-
senting known subjects (birds, fishes) or objects (letter shapes), we
define the evolving screen dot shape by a description of its contours.
For this purpose, weintroduce fixed predefined screen dot contours
which are associated with specific intensity levels. Shape blending
techniques [15] are used to interpolate between those predefined
screen dot contours at all other intensity levels.
The fixed predefined contours, defined in a screen element def-
c) interpolated contours
SIGGRAPH'95 Computer Graphics Proceedings, Annual Conference Series, 1995
Figure 11: Screen tile containing subscreen shapes made of individual characters, at different intensity levels.
inition space, are designed by a graphist using a shape drafting
software package such as Adobe Illustrator. The graphist defines
his contours in the screen element definition coordinate space of
his preference. Figure 9a shows a set of fixed predefined contours
defining the evolution of a screen dot shape.
For ease of implementation, we assume that each fixed contour
has the same number of distinct contour parts and that the contour
parts of the interpolated contours are obtained by blending between
corresponding fixed contour parts. Curved contour parts may be
described by polynomial splines. For convenience, we use a cubic
Bézier spline given by its control polygon to define each curved
contour part. In order to simplify the interpolation process, we
also assume that each straight line contour part is also defined by
Bézier control polygon having its vertices aligned on the given
straight line segment. The arrangement of contour parts in each
of the fixed predefined contours governs the interpolation process
(Fig. 9).
Screen element Screen element
definition space rendition space
Figure 10: Transformation between screen element definition and
rendition space (a) applied to a small screen tile and (b) applied
to a large screen tile (super screen) made of repetitive subscreen
In order to control the speed at which the interpolated contour
parts move from one fixed contour to the next, we introduce inter-
polation parameters κ
(z)varying between 0 and 1 (Fig. 9d). The
coordinates of a control point at intensity zinterpolated between
two fixed contour control points and associated with the
extremities of intensity range [z
, z
] is given by
where represents the screen element origin.
Parameters κ
(z) are mapped to the range of intensity levels
, z
] by interactivelydefining the curves κ
(z) in the same way
as gamma correction curves are defined in well known grayscale
halftoning packages (Adobe Photoshop for example). Figure 9
shows the full intensity range, fixed predefined and intermediate
contours as well as their associated interpolation parameters.
In the range between intensity level z
= 0 and intensity level
associated with the first fixed contour, the only operation which
takes place is scaling. Wetherefore assume that the contour at level
is a fixed contour of infinitely small size and that it has the same
number of control points as the one at level z
The tone reproduction behavior of a given printing process de-
pends heavily on the dot gain, i.e. to what extent the printed dot
has a larger surface than expected due to printer toner or ink spread
properties. For a given printing process, the tone reproduction be-
havior depends on the shape of the printed dot. When increasing
the darkness (or, equivalently, decreasing the intensity) at light and
mid-tones, the relative printed surface increase is larger for dots
having a higher contour to surface ratio. Since the fixed contours
defining the artistic screen dot shape may have any contour to sur-
face ratio, the surface growth of the printed dot for a given intensity
difference may vary considerably at different intensity levels. We
can therefore use interpolation parameters κ
(z)as local gamma
correction factors [4].
If the created screen element is required to have a similarshape
growing behavior in the light and in the dark tones, one may first
design the fixedscreen dot contoursin the lighttones and thenin the
dark tones. Taking into account the plane tiling behavior of a single
screen element, the fixed contours associated with intensity levels,
z 0.5 are drawn at a location whose center is translated by half
a period in each direction from the original screen element center.
The fixed contour parts located on the three quadrants outside the
original screen element boundary are copied back into the original
screen element (see Fig. 9a, 50% intensity).
A single fixed contour associated with an intensity level equal
to or close to z = 0.5 delimits the white growing region and the
black growing region.
Onceall fixed contourshave beendesigned inthe screenelement
definition space, and the table of blending parameters is initalized
P(z) -
= (1 - κ
(z)) (P
) + κ
SIGGRAPH'95 Computer Graphics Proceedings, Annual Conference Series, 1995
a) b) c)
-2 -1 1 2
-1 -0.5 0.5 1
Figure 12: Non-linear mapping between screen definition and screen rendition plane.
with values κ
(z), one merely needs to define the corresponding
screen element boundaries in the screen element rendition space,
e.g. in the space associated with the output bitmap. The transfor-
mation between screen element definition space and screen element
rendition space enables the fixed predefined screen dot contours to
be defined independently of the orientation and size of the final
screen elements (Fig. 10). This transformation provides the basis
both for screen element morphing (see Section 4) and for the gen-
eration of screen elements having exact screen angles, as required
by traditional colour reproduction techniques [19].
A square screen element defined by its supporting cathets
and (Fig. 10b) whose desired orientation is given by angle can
be approximatedby anangle α' = arctan
( )
as closely as required
by increasing integer values dx and dy . The screen element's sub-
division into a certain number of replicated subscreen dot shapes
defines its screen frequency. In the screen element definition space,
all subscreen dot shapes are identical. In the screen element ren-
dition space however, rasterized discrete subscreen elements differ
slightly one from another due to the different phase locations of
their respective continuous contours (Fig. 10b). At high resolution,
the so obtained exact angle screen elements are equivalent to the
super-screening methods known in the field of colour reproduction
[2], [13]. They have the advantage of offering the potential for
colour reproduction with specifically designed screen shapes.
Once the fixed predefined contour parts have been transformed
from screen element definition to rendition space, the discrete
screen elements may be generated for each discrete intensity level.
For reproducing 256 intensity levels, the intensity interval be-
tween z = 0 and z = 1 is divided by 255 and intermediate
screen dot contours are successively generated at intensity levels
z = 0, z = 1 / 255, …, z = 255 / 255. At each discrete intensity, the
screen dot contours are rasterized by applying well known shape
rasterization techniques [4]. In the case of self-intersecting dot
contours or dot contours having at a single intensity level multiple
intersecting contours, care must be taken to use a scan-conversion
and filling algorithm supporting the non-zero winding number rule
andgenerating non-overlapping complementarydiscreteshapes[5].
Furthermore, the fillingalgorithm mustbe able to fillshapes becom-
ing smaller and smaller until they disappear [6]. Figure 6 shows the
result with an artistic screen dot shape inspired by Escher's drawing
(Fig. 1a), reproduced on a grayscale wedge. Small details, such as
the wings of the bird, progressively fade out as the bird's shape size
4 Screen Morphing
Sincescreen tiles canbe aslarge asdesired, theycan beconceived so
as to cover either the whole or a significant part of the surface of the
destination halftoned image. Such large screen tiles aredivided into
elementary subscreen shapes which may contain either identical or
different shapes. For microlettering applications, each elementary
subscreen shape may contain a different letter shape (Fig.11).
By defining the mapping from screen element definition space
to screen element rendition space as a non-linear transformation,
smooth, highly esthetic spatial variations of the subscreen shapes
can be attained. For example, conformal mappings [14] [3] trans-
form a rectangular grid of screen element sub-shapes into the sub-
shapes of a deformed grid following electro-magnetic field lines
(Fig. 12a). In that example, the conformal mapping is w =
k(1 + z + e
), where k is a real scaling factor, z represents complex
points z = x + iy lying in theoriginal (x, y) plane and w = u + iv
the corresponding complex points lying in the destination (u, v)
Alternatively, if one would like to enlarge a few screen sub-
shapes at the expense of their surrounding subshapes, one may
define a circle of unit radius within which a geometric transforma-
tion maps the original rectangular grid into a highly deformed grid
(Fig. 12b). A possible transformation is one thatkeeps the angle and
modifies the distance of points from the center of the circle (fisheye
transformation). With the center of the circle as the origin of the
coordinate system, the mapping expressed in polar coordinates is
the following:
θ' = θ;
1 - r
1 +
m *
if r < 1
otherwise (2)
where mis a magnifying factor.
r' = r
1 - r
m *
SIGGRAPH'95 Computer Graphics Proceedings, Annual Conference Series, 1995
Figure 13: View of the Ibn Tulun Mosque, Cairo (Courtesy of R. and S. Michaud, Rapho).
5 High-quality artistic screening
In high-quality graphic applications, the shapes of artistic screen
dots may be used as a vector for conveying additional information.
This new layer of information may incorporate shapes which are
related to the image. When reproduced in poster form, the screen
elements of the screening layer will become sufficiently large to
produce the desired visual effect.
In Figure 13, we show an example of a mosque rendered by
screen dots made of calligraphic arabic letter shapes and oriental
polygonal patterns. This screening layer adds a touch of islamic
culture to the reproduced image.
The next example (Fig. 14) shows a poster displaying a scene
inspired from the well-known Kabuki theater shows. Such a poster
could be used for example to advertise a Kabuki theatre perfor-
mance. The beautiful Kanji letter shapes can be seen close up
whereas the full poster can only be perceived from a certain view-
ing distance. These two different views complement one another
and each contributes towards transmitting the message to the public.
In the last example, we show that artistic screening can bring
new solutions for avoiding desktop counterfeiting [16]. Since
1990, the US treasury protects banknotes by using microprinting
techniques for generating letters having a size of approximatively
150 µm in order to avoid reproduction by photocopy or scanners
(Fig. 15). In Figure 16, we show that by using artistic screen-
ing techniques, microletters of the type shown in Figure 11 can
be incorporated into the grayscale image. Furthermore, due to the
conformal mapping function w = tg(z) between screen element
definition and rendition spaces (Fig. 12c), a non-repetitive screen
is created which cannot be scanned easily without producing Moiré
6 Conclusions
We have presented a new halftoning technique, where screen ele-
ments are composed of artistic screen dot shapes, themselves cre-
ated by skilled graphists. Fixed predefined dot contours associated
with given intensity levels determine the screen dot shape's grow-
ing behavior. Screen dot contours associated with each intensity
level are obtained by interpolation between the fixed predefined
dot contours. User-defined mappings transform screen elements
from screen element definition space to screen element rendition
space. These mappings can be tuned to produce various effects
such as dilations, contractions and non-linear deformations of the
subscreen element grid. By choosing an appropriate mapping, im-
ages can be rendered while ensuring a highly esthetic behavior of
their screening layer.
Since artistic screening uses precomputed screen elements, its
performance at image halftoning time is similar to that of other
dithering algorithms. The time required for precomputing the
screen elements associated with every intensity level depends on
the size of the screen element tile. Limited size repetitive screen
elements such as those used in Figures 13 and 14 can be gener-
ated quickly (few minutes). On the other hand, very large screen
elements morphed over the output image may require considerable
computing power and time. Therefore, libraries of precomputed
screen elements should be created. With such libraries, artistic
screening can be made nearly as efficient as conventional halfton-
ing.Artistic screening can be seen as a new image reproduction
technique incorporating freely created artistic screen elements used
for generating halftones. Since both the image to be reproduced
and the screen shapes can be designed independently, the design
freedom offered to artists is very great. In the examples of sections
4 and 5, we have shown that one may reproduce simple images with
complicated screen elements morphed over the destination halftone
image, real images with beautiful but repetitive screen shapes or
SIGGRAPH'95 Computer Graphics Proceedings, Annual Conference Series, 1995
Figure 14: Kabuki actor, by Toshusai Sharaku. Scene inspired from the Japanese Kabuki theater. The word Kabuki,
shin-ka-bu-ki, is used for creating the Kanji screen dot shape (Courtesy of the British Museum).
real images with complicated and morphed screen shapes.
Artistic screening enables both full size and microscopic letters
to be incorporated into the image reproduction process. For exam-
ple, next-generation banknotes may incorporate grayscale images
with intensity levels produced by microletters of varying size and
Currently, artisticscreening is made possible by creating screen
shapes with existing shape outlining tools and feeding them as input
to the artistic screening software package. In the near future, we
intend to add specific screen shape creation and morphing tools
in order to simplify the design of the fixed predefined screen dot
contours and the specification of the transformation between screen
element definition and screen element rendition space.
Thanks to these novel computer-based screening techniques,
artistic screening may become an important graphic design tool. It
may have a considerable impact on future graphic designs.
SIGGRAPH'95 Computer Graphics Proceedings, Annual Conference Series, 1995
Figure 15: Microletters on current ten dollar notes.
7 Acknowledgements
We would like to thank Nicolas Rudaz for having developed the
QuickTime animation illustrating the basic concepts of Artistic
Screening (see SIGGRAPH'95 Proceedings on CD-ROM). We are
grateful to H. Massoudy, Bella O.,the British Museum, Rapho Press
Agency, Paris and Cordon Art, Baarn, Holland for having kindly
accepted to give us the permission to reproduce their originals.
[1] K. Critchlow, Islamic Patterns, Thames & Hudson, 1989.
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SIGGRAPH'95 Computer Graphics Proceedings, Annual Conference Series, 1995
Figure 17: The vignette shown in Fig. 16, enlarged 4 times.
SIGGRAPH'95 Computer Graphics Proceedings, Annual Conference Series, 1995
... Stippling techniques for artistic screening were proposed by Ostromoukhov et al. [42] based on the predefined dot contours and certain intensity level. Intensity level was obtained via interpolation. ...
... They were adopted for color conversion purpose to produce multi-level color halftoning. Multi-color and Artistic Dithering technique was proposed by Ostromoukhov [44] in 1999 based on multi-color dithering algorithm and it extended the previous proposed works [42,43]. ...
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This survey presents a comprehensive study on non-photorealistic rendering (NPR). NPR technique renders 2D input image into abstracted and artistic stylized images. NPR mainly dwells on image processing, computer vision, and visualizing the graphics processing techniques. The survey highlights the evolution of IA–AR system and the subsequent classification of NPR techniques. The survey also has cognized the various works done on stroke-based rendering, color image analogy, region-based rendering, image filtering abstraction, and stylization. The inference drawn from the survey is the computer system using a stylus to fully automatic structure-preserving image abstraction and stylization got evolved from a traditional method of human interaction. From the survey carried out on the most significant papers from 1963 to 2017, we felt the need for setting up of benchmark guidelines, the data set with varies subjective matters, and quality assessment techniques with various statistical essences. From the survey information pertaining to benchmark image characteristics, properties and their constraints with the contextual feature in an image have been identified. Finally, survey work listed out the NPR application in various fields of image processing and highlighted empirical challenges and hampers in NPR domain. This survey work has empowered us to proceed in the right direction and enthusiasm to bring forth the problem statement and carry out research work.
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This paper proposes a method for changing pixel shape by converting a CMYK raster image (pixel) to an HSB vector image, replacing the square cells of the CMYK pixels with different vector shapes. The replacement of a pixel by the selected vector shape is done depending on the detected color values for each pixel. The CMYK values are first converted to the corresponding RGB values and then to the HSB system, and the vector shape is selected based on the obtained hue values. The vector shape is drawn in the defined space, according to the row and column matrix of the pixels of the original CMYK image. Twenty-one vector shapes are introduced to replace the pixels depending on the hue. The pixels of each hue are replaced by a different shape. The application of this conversion has its greatest value in the creation of security graphics for printed documents and the individualization of digital artwork by creating structured patterns based on the hue.
Line drawing and screentoning are two distinct areas of study in non-photorealistic rendering, where the former emphasizes object contours, while the latter conveys tone and shading information on object surfaces. As these two problems are concerned with different yet equally important features, either method seldom delivers a complete description of the scene when used alone. Yet, research community has largely treated them as separate problems and thus resulted in two entirely different sets of solutions, complicating both implementation and usage. In this paper, we present a stylistic image binarization method called hybrid difference of Gaussians (HDoG) that performs both line drawing and screentoning in a unified framework. Our method is based upon two different extensions of DoG operator: one for line extraction, and the other for tone description. In particular, we propose an extension called adaptive DoG, that uses luminance as weight to automatically generate screentone that adapts to the local tone. Experimental results demonstrate that our hybrid method effectively generates aesthetically pleasing image binarizations that encompass both line drawing and screentoning, closely resembling professional pen-and-ink illustrations. Also, being based on Gaussian filtering, our method is very fast and also easy to implement.
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Artistic screening is a new halftone technology for producing an illusion of continuous tones by creating artistic screens that may take any desired shape and screening effects. This screening technology is tuned to convey additional information for artistic purposes, which is desirable for digital anti-counterfeiting in today’s printing industry. In order to achieve better anti-counterfeiting results, a novel data hiding algorithm is proposed by combining the artistic screening technology with digital watermarking. We present a digital watermarking algorithm in artistic screening images that divides the images into blocks and embeds a fixed number of bits in each block by changing some pixels in that block. Experiments show that watermarking-embedded artistic screening image is good at securing data hiding results and tampering of content can be detected successfully.
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In the field of computer graphics there is an increasing demand for non-photorealistic effects. We add the idea of pattern recognition guided by theoretical rules into a traditional NPR system and create non-photorealistic drawings intelligently. The Style Sample Library functions as an expert library and makes it easier to render a picture with nonphotorealistic effects even by an amateur user
The history of halftoning technology is presented as revealed in the U.S. patent literature, with emphasis on clustered dot halftoning. With the goal of gaining insight into current trends in halftoning, I have partitioned the history into four eras, and have categorized halftoning patents by their 'scores' of a checklist of five factors that can influence the decision to turn on a microdot to construct a halftone dot. I have learned these lessons: First, both of the two major halftoning technologies have their origins in early work. The 19th century work on classical screening underlying today's electronic clustered dot halftoning is perhaps better known than work at RCA in the 1920s underlying error diffusion. Second, digital electronic halftoning by thresholding, currently the dominant technique for clustered-dot halftoning, suffers in some respects by comparison to two of its antecedents. To overcome these problems the initially elegant machinery of halftoning by thresholding has been encumbered with inelegant modifications. Third, these problems also create an incentive for fundamental innovations. Two prominent ways of doing this are to extend the list of factors that influence the decision to turn on a microdot, or to use irregular dot locations (as is already done in the dispersed dot techniques).
Modern personal computers and workstations enable text, graphics and images to be visualized in a resolution independent manner. Office documents can be visualized and printed in the same way on displays, page-printers and photocomposers. Personal computers like the PC and the MacIntosh incorporate advanced rasterization algorithms for the rendering of outline characters and graphics. In the nineties, advanced workstations will provide facilities for the generation of finely tuned gray-scale characters. This tutorial provides a survey of the basic algorithms for representing and rendering outline characters. Fast scan-conversion and filling algorithms as well as basic and advanced character outline grid-fitting techniques are presented. The philosophy and functionality of Adobe's Type 1 and Apple's TrueType typographic rendering systems are discussed.
This paper describes the principles of traditional pen-and-ink illustration, and shows how a great number of them can be implemented as part of an automated rendering system. It introduces "stroke textures," which can be used for achieving both texture and tone with line drawing. Stroke textures also allow resolution-dependent rendering, in which the choice of strokes used in an illustration is appropriately tied to the resolution of the target medium. We demonstrate these techniques using complex architectural models, including Frank Lloyd Wright's "Robie House." Computer-Generated Pen-and-Ink Illustration Georges Winkenbach David H. Salesin Department of Computer Science and Engineering University of Washington Seattle, Washington 98195 Abstract This paper describes the principles of traditional pen-and-ink illustration, and shows how a great number of them can be implemented as part of an automated rendering system. It introduces "stroke textures, " which can be used for...