Computer graphics processing and selective visual display system – Computer graphics processing – Attributes
Reexamination Certificate
2001-10-25
2004-05-18
Bella, Matthew C. (Department: 2676)
Computer graphics processing and selective visual display system
Computer graphics processing
Attributes
Reexamination Certificate
active
06738071
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the presentation of computer graphics. Particularly, the present invention relates to the dynamic anti-aliasing of computer graphics.
DESCRIPTION OF THE RELATED ART
Anti-aliasing on a display device, such as a computer monitor or printer where the display surface is divided into a rectangular array of pixels, solves the problems inherent with drawing lines and curves. Anytime a line changes direction, a jagged stair-step pattern occurs.
A typical prior art jagged edge of a letter is illustrated in FIG.
1
. This figures shows that as the bottom of the “J” curves upward, the square pixels produce a jagged appearance. This problem can be reduced with fonts by using an anti-aliasing process on the font.
Anti-aliasing works by blending foreground and background colors near jagged edges. This “softens” the edges of the font when the lines change direction.
FIG. 2
illustrates a typical prior art anti-aliasing of a font. In this figure, it can be seen that the black text color is “averaged” with the background color to reduce the appearance of the jagged edge.
The anti-aliasing color that was generated for
FIG. 2
is embedded in the graphic description and becomes part of the color description information for that graphic. When the graphic is moved to another background, the same anti-aliasing colors are used. If the background is comprised of a color or colors that are different than the original color, the edges of the graphic will not blend well with the new background color and the graphic may end up with an undesirable appearance along the edges. There is a resulting need for a process for anti-aliasing a graphic that enables the graphic to be moved to various background colors without affecting the appearance of the graphic.
SUMMARY OF THE INVENTION
The present invention encompasses a method and apparatus for anti-aliasing a graphic image. An image layer is generated for the graphic image, the image layer comprising a plurality of pixels, each pixel including a red, a green, and a blue component. An opacity value is assigned to each pixel of the plurality of pixels in order to generate an alpha channel layer. The alpha channel layer is stored with the image layer.
REFERENCES:
patent: 5519823 (1996-05-01), Barkans
patent: 5982381 (1999-11-01), Joshi et al.
patent: 6426755 (2002-07-01), Deering
patent: 2002/0122036 (2002-09-01), Sasaki
patent: 2003/0107583 (2003-06-01), Fushiki et al.
Foley et al., “Computer Graphics: Principles and Practice”, 1990, Addiso-Wesley, Second Edition, pp. 754-755.
Bella Matthew C.
Cunningham G. F.
Hewlett--Packard Development Company, L.P.
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