Antialiasing
jaggies
digitized
Analog line
Digital line: aliasing occurs
Aliased 'W'
Antialiased 'W'
168 471 Computer Graphics, KKU. Lecture 9
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Antialiasing
What anti-aliasing attempts to do
is, using mathematics, fill in some
of the digital system with colors
that are in-between the two
adjoining colors. In this case a
medium gray would be between
the black and the white. Some
gray squares placed in the grid
might help soften up the "jaggies"
168 471 Computer Graphics, KKU. Lecture 9
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Antialiasing
168 471 Computer Graphics, KKU. Lecture 9
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Unweighted Area Sampling
• Intensity is proportional to the amount of area covered.
• Defining the box weighting function which has volume of 1 (Imax).
• Determine the overlap volume Ws [0, 1].
•
168 471 Computer Graphics, KKU. Lecture 9
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Weighted Area Sampling
168 471 Computer Graphics, KKU. Lecture 9
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Antialiasing in Practice
• Use of low pass filter by summing products between the mask
coefficients and the intensities of the pixels under the mask.
• For w which is a 3x3 mask, the response R at the center of
the mask is
R = w1z1 + w2z2 + … + w9z9
mask
R
mask
168 471 Computer Graphics, KKU. Lecture 9
R
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Antialiasing in Practice
(a)
168 471 Computer Graphics, KKU. Lecture 9
(b)
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