First color film - 1902

• Captured by Edward Raymond Turner

• Predates Prokudin-Gorskii collection

• Like Prokudin-Gorskii, it was an additive 3-color system.

• Never successfully commercialized

Recap of Friday

Sampling and ReconstructionAliasing and how to prevent it (blur / low pass filters)

Linear filtering and convolution

Slides from Alexei Efros, Fei Fei Li, Steve Marschner, and others

Linear Filtering (See Szeliski 3.2)

CS 129: Computational Photography

James Hays, Brown, Spring 2011

Slide credit Fei Fei Li

Slide credit Fei Fei Li

Slide credit Fei Fei Li

Slide credit Fei Fei Li

-2.6-0.33

1.6610.66

© 2006 Steve Marschner • 40

A gallery of filters

• Box filter– Simple and cheap

• Tent filter– Linear interpolation

• Gaussian filter– Very smooth antialiasing

filter

• B-spline cubic– Very smooth

© 2006 Steve Marschner • 41

Box filter

© 2006 Steve Marschner • 42

© 2006 Steve Marschner • 43

© 2006 Steve Marschner • 44

© 2006 Steve Marschner • 48

Yucky details

• What about near the edge?– the filter window falls off the edge of the image– need to extrapolate– methods:

• clip filter (black)• wrap around• copy edge• reflect across edge• vary filter near edge

© 2006 Steve Marschner • 49

Median filters

• A Median Filter operates over a window by selecting the median intensity in the window.

• What advantage does a median filter have over a mean filter?

• Is a median filter a kind of convolution?

Slide by Steve Seitz

© 2006 Steve Marschner • 50

Comparison: salt and pepper noise

Slide by Steve Seitz