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Anti-Aliased Text
Anti-aliasing is a method of drawing text or pictures which smooths
edges, and avoids jagged edges ("jaggies").
In this article we'll discuss
anti-aliasing as applied to drawing
text.
Imagine that we wish to place a character
glyph from
an outline font on a bitmap.
Looking at it closely (enlarging so that you can see the individual
pixels), it might look something like this
example:
| Overlaying a Glyph on a Pixel Grid |
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There is an obvious problem, if you look closely at the above diagram.
Namely, when we try to convert the glyph to
a bitmap ("rasterise"),
we can only have a single color for each
individual pixel, but some of the cells in
the pixel grid contain both red and white.
So how do we address this problem?
A simple solution (not anti-aliased) would be to look at each
pixel cell:
- If the pixel cell contains nothing but white, we
make the pixel white.
- If the pixel cell contains nothing but red, we
make the pixel red.
- If the pixel cell contains both red and white,
we can choose to
make the pixel red or white.
For example, we might choose
whichever color covers a larger proportion of the cell.
Here's an example of how this might look:
The Glyph Rasterised
Not Anti-Aliased |
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That isn't bad, but as you can see, it does look a little bit jagged
(see "Jaggies").
This problem can be addressed by modifying our method of
rasterising the glyph.
This new method (anti-aliasing) works:
- As before: If the pixel cell contains nothing but white, we
make the pixel white.
- As before: If the pixel cell contains nothing but red, we
make the pixel red.
- However: If the pixel cell contains both red and white,
we make the pixel an intermediate color
between red or white (a lighter shade of red).
- The more white in the
pixel cell,
the lighter (more whitish) we make the final pixel color.
- The more red in the
pixel cell,
the redder we make the final pixel color.
Here is the result it produces:
The Glyph Rasterised
Anti-Aliased |
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This time, it doesn't look jagged, but it does (to some eyes at least),
look a little blurred. This difference will become clearer when we
compare the images at their final sizes.
Finally, here is a comparison, at actual size, of text which has
been anti-aliased, and text which has not been.
(I have also included a comparison between two blocks of black and white
text - in this case, the anti-aliasing is done using shades of gray rather
than red).
| Not Anti-Aliased |
Anti-Aliased |
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Related Pages on this site:
Related Books:
- Computer Graphics Dictionary (Advances in Computer Graphics and Game Development Series)
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Charles River Media
Hardcover (460 pages)
Product Description:
The popularity of special effects movies and video games has introduced thousands of new terms, techniques, and software applications to both the computing professional and the general user. These graphics creations represent a convergence of expertise from several subject areas, resulting in a lack of familiarity with many terms. This unique dictionary is a comprehensive reference for the diverse fields of computer graphics and game development. It includes over 4,000 definitions and 1,000 illustrations. KEY FEATURES * Includes a companion CD-ROM with over 1,000 full color images, animations, movies, and additional explanatory items * Provides a reference for computer graphics and game development, defining terms and references seldom found in other computer dictionaries * Also defines terms and techniques from popular software applications SYSTEM REQUIREMENTS General Minimum Requirements. PC: 486 or higher; Windows 95 or later; MAC OS 8.5 or later; 16 MB RAM; CD-ROM drive; Web browser; mouse or pointing device; VGA monitor. Illustration files (e.g., .jpeg, .tiff, etc.) require a graphics viewing application. Many animated files on the CD-ROM require their respective graphics applications.
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Related Software:
- FontTwister
FontTwister is the fastest and easiest way to create dazzling text effects. FontTwister comes with an impressive selection of templates for graphic styles, color gradients, textures, shapes, letter edges, 3-D bevels, shadows, buttons and frames. Simple intuitive controls let you interactively real-time view and select your desired effect. You can re-edit text and effects at any time. The effect generator creates unlimited variations of amazing text effects.
Use high impact, anti-aliased text for logos, 2D and 3D headings in letters, presentations, flyers, invitations, cards, faxes, posters, web graphics, labels, banners, buttons, covers. FontTwister supports several popular image formats (.bmp, .jpg, .png, .tif, .wmf).
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