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21
ALIASING
21
Aliasing
21.1
Aliasing
Aliasing and Anti-Aliasing
• Raster Image is a sampling of a continuous function
• If samples spaced too far apart, then don’t get true representation of scene:
• In graphics, a variety of bad things happen:
– Stairstep or “jaggies”
– Moire Patterns
– Loss of small objects
– Temporal
∗ Sampled too far apart in time
Backwards rotating wheels
∗ Crawling jaggies
∗ Appearing/dissappearing objects, flashing objects
Image as a signal
• Signal processing signal is function of time
• Scene is a function of space
Spatial domain: f (u)
• Raster image is a sampling of this signal
• Can represent signal as sum of sine waves
Frequency domain: F (u)
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