Color

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7

Slide 65

Contrast effects

Slide 66

After images

Tired photoreceptors send out negative response after a strong stimulus

Source: Steve Seitz

Slide 67

Name that color

High level interactions affect perception and processing.

Slide 68

Today: Color

Measuring color

Spectral power distributions

Color mixing

Color matching experiments

Color spaces

Uniform color spaces

Perception of color

Human photoreceptors

Environmental effects, adaptation

Using color in machine vision systems

Slide 69

Color as a low-level cue for CBIR

Blobworld system

Carson et al, 1999

Swain and Ballard, Color Indexing, IJCV 1991

Slide 70

R

G

B

Color histograms: Use distribution of colors to describe image

No spatial info – invariant to translation, rotation, scale

Color intensity

Pixel counts

Color as a low-level cue for CBIR

Slide 71

Color-based image retrieval

Given collection (database) of images:

Extract and store one color histogram per image

Given new query image:

Extract its color histogram

For each database image:

Compute intersection between query histogram and database histogram

Sort intersection values (highest score = most similar)

Rank database items relative to query based on this sorted order

Slide 72

Color-based image retrieval

Example database

Slide 73

Example retrievals

Color-based image retrieval

Slide 74

Example retrievals

Color-based image retrieval

Slide 75

Slide 76

Color-based skin detection

M. Jones and J. Rehg, Statistical Color Models with Application to Skin Detection, IJCV 2002.

Slide 77

Color-based segmentation for robot soccer

Towards Eliminating Manual Color Calibration at RoboCup. Mohan Sridharan and Peter Stone. RoboCup-2005: Robot Soccer World Cup IX, Springer Verlag, 2006