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Dithering
Dithering is an imaging technique which allows a
bitmap (or a
bitmapped device,
such as a screen or printer) to appear to
display more colors than are actually possible.
- If the bitmap
(or bitmapped device)
only allows black and white, dithering can be used to produce
an illusion of gray.
- If the bitmap
(or bitmapped device)
allows a palette of colors,
then dithering can produce an illusion of more colors
being displayed than are in the palette.
Let's look at some examples (on the left I show a zoomed in
section of bitmap, on the right
I show a larger section of bitmap at
actual size.
Using black and white to produce the illusion of light gray:
Zoomed In
25% Black, 75% White |
|
Actual Size
Dithered Image |
 |
|
|
Using black and white to produce the illusion of a mid gray:
Zoomed In
50% Black, 50% White |
|
Actual Size
Dithered Image |
|
|
|
Using black and white to produce the illusion of a dark gray:
Zoomed In
75% Black, 25% White |
|
Actual Size
Dithered Image |
|
|
|
Using red and yellow to produce the illusion of a orange:
Zoomed In
50% Red, 50% Yellow |
|
Actual Size
Dithered Image |
|
|
|
While dithering is an effective technique for making an image
look as if it has more colors, there are a number of issues with dithering:
- Some methods of dithering can produce the illusion of patterns
within the colored areas. This can be a significant problem when
dithering images containing naturalistic images (for example,
photographs), and tends to be particularly
noticeable when dithering is used on
relatively low resolution
devices.
- Various methods of dithering have been devised (some of which
may produce less obvious patterning than others). These include:
- Once an image has been dithered, it can be extremely hard to
edit.
For example, if we had an image which contained areas that
had been dithered (like the examples above) to produce orange
and various shades of gray, there is no simple way to adjust the
color of those areas, because each area contains a mix of
pixels of different colors.
As a result, in an ideal world, images would be prepared and stored
in full color, and then only dithered when displayed/printed on a device
which did not support all the necessary colors. However, in the
real world, the limitations of networks, storage, memory, and
graphics file formats, frequently means that despite this
significant disadvantage, images are often prepared and stored already
dithered.
- Dithered images contain lots of fine detail that may not
compress well, particularly in file formats
that use LZW or
Run-length Compression.
As a result, in some cases, it may actually take less storage
and bandwidth to store and transmit images in full
TrueColor, and allow the output
device to perform any necessary dithering upon receiving this image.
An example where this may occur is if web publishing images
in PNG format.
Related Pages on this site:
Related Books:
- A Visual Dictionary of Graphic Design
Disclosure: Products details and descriptions provided by Amazon.com. Our company may receive a payment if you purchase products from them after following a link from this website.
| |
By Gavin Ambrose
Ava Publishing
Released: 2006-11-15
Paperback (288 pages)
Product Description:
Abstract. Zeitgeist. Bauhaus. Pluralism. The Visual Dictionary is just the book for anyone who's ever been a bit hazy about the meaning of the many terms used in art and design. Each term is explained visually and put in context, providing the reader with a clear understanding of the often mystifying language of these specialized fields. To help the reader understand and remember the meanings, each entry uses a different typeface (a history of the fonts is in the back of the book) and includes a picture in an appropriate illustration techniques. Eclectic, useful, and entertaining, The Visual Dictionary takes the complex and makes it simple.
List Price: $24.95*
Lowest New Price: $11.99*
Lowest Used Price: $2.45*
Usually ships in 24 hours*
*(As of 17:42 Pacific 3 Feb 2012 More Info)
Buy It Now
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- Computer Graphics Dictionary (Advances in Computer Graphics and Game Development Series)
Disclosure: Products details and descriptions provided by Amazon.com. Our company may receive a payment if you purchase products from them after following a link from this website.
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By Roger Stevens
Charles River Media
Hardcover (460 pages)
Product Description:
The popularity of special effects movies and the video game industry has introduced thousands of new terms, techniques, and software applications to both the computing professional and the general user. Unfortunately, these graphics creations represent a convergence of expertise from several different subject areas, resulting in a lack of familiarity with many terms. This unique dictionary includes over 4,000 definitions and illustrations from the computer graphics world, including those from digital filmmaking, animation, programming, mathematics, holography, photorealism, lighting, character creation, game development, modeling, and more.
List Price: $49.95*
Lowest New Price: $29.95*
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- Graphic Design Speak: A Visual Dictionary for Clients and Designers
Disclosure: Products details and descriptions provided by Amazon.com. Our company may receive a payment if you purchase products from them after following a link from this website.
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By Anistatia R. Miller
Rockport Publishers
Hardcover (160 pages)
Product Description:
What does a client or art director really mean when they say "I want a clean look" or "The design should be bold"? Graphic Design Speak offers the answers in an easy-to-follow format that both clients and designers can use as points of reference in design briefs or strategy meetings. This book is an essential tool for any designer seeking to gain a better knowledge of the wants and needs of their clients. --Over 200 color projects showing specific design solutions to answer client demands --An international gathering of designers, studios, and ad agencies --Quotes, tips, and anecdotes from both designers and clients
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