04/18/2002
15-462 Graphics I
33
Exploiting Interpixel Redundancy
•Neighboring pixels are correlated
•Spatial methods for low-noise
image
–Run-length coding:
•Alternate values and run-length
•Good if horizontal neighbors are
same
•Can be 1D or 2D (e.g. used in fax
standard)
–Quadtrees:
•Recursively subdivide until cells are
constant color
–Region encoding:
•Represent boundary curves of
color-constant regions
•Combine methods
•Not good on natural images directly