Camouflage Detection

1
Camouflage Detection

• An introduction
• Presented by Ani Starrenburg

2
General Camouflaging Strategies

• Cryptic Camouflage

Little Button Quail
Traditional US Army Camouflage Pattern
3
General Camouflaging Strategies

• Mimicry

Rose Greenbow, Confederate Spy
Dronefly
4
General Camouflaging Strategies

• Disruption

Dazzle Camouflage
Sumatran Tiger
5
General Camouflaging Strategies

• Countershading

Impala
Non-Countershaded Warship
6
General Camouflaging Strategies

• Translucence/Transparency

Seawasp
Invisibility Cloak
7
Detecting Camouflaged Objects
8
Camouflage Detection Methods

• Standard Object Detection Methods
• Edge Detection Models
• Contrast Energy Detection Model
• Motion Detection
• Correlation Models
• Gradient Models
• Energy Models

9
Edge Detectors
Laplacian
Laplacian With Gaussian
Gradient
Gaussian
10
Canny Detector

• Optimal Edge Detector
• Multiple Stage Algorithm
• Perform Gaussian smoothing
• Find edge strengths
• G Gx Gy
• Detection of edge direction
• theta invtan(Gy/Gx)
• Relate edge direction to
• a direction that can be traced
• in an image
• Apply non-maximum
• suppression
• Use hysteresis to eliminate streaking

11
LaPlacian or LoG

• Smooth with a Gaussian mask
• Calculate the second derivatives
• Search for zero crossings
• Or
• Convolve the image with the
• Laplacian of the Gaussian

12
Contrast Energy (CE) Model

• Uses the output signal from similarly-oriented
• odd ox and even ex filters.
• Energy function is defined as
• E2(x) e2(x) o2(x)
• Always positive
• Shows high output when o(x), e(x) or both are
  high.

13
Camouflage DetectionMethods to be Discussed

• Convexity-Based Detection exploits the
  principle of countershading to detect camouflaged
  objects
• Texture Detection intensive texture analysis
  distinguishes camouflaged object from background.
  Also, uses Canny detector to bring up edges

14
Motion Breaks Camouflage
Region of common velocity is perceived As a unit
and stands out against the static background
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Reichardt Correlation Model

• Computes motion as the ratio of the partial
  derivatives of the input image brightness with
  respect to space and time.
• Two spatially-separate detectors.
• Output of one of the detectors is delayed.
• The two outputs are multiplied to determine if
  there is a correlation.

16
Multichannel Gradient Model

• Uses multiple channels of higher derivatives
• The more derivatives used lowers the chance of
  that all will be zero at the same time
• Uses a least sqaures approximation of the
  derivatives

17
Motion Energy Model

• Uses two sets of oriented detectors(leftwards and
  rightwards), each composed of an odd and an even
  filter.
• Energy is calculated by summing the squares of
  the two similarly-oriented filters.
• Calculate opponent energy (difference of leftward
  and rightward results)
• Normalize by dividing by static energy to give
  velocity estimates

18
An aside Research on Active Camouflage

• Animals that can escape edge detection
• Animals that can camouflage motion

19
To Do List

• Apply edge detectors and contrast energy
  detectors to camouflaged and illusory images and
  view results.
• Research visual models developed from observing
  animal behavior and development.
• Research studies in psychology for further
  understanding of vision process.

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Is there a core visual system?
C A M O U F L A G E
A R T
21
Bibliography

• Motion Illusions and Active Camouflage, Lewis
  Dartnell ,http//www.ucl.ac.uk/ucbplrd/motion/mot
  ion_middle.html
• Canny Edge Detection Tutorial, Bill Green,
  http//www.pages.drexel.edu/weg22/can_tut.html
• Honeybee, http//www.gpnc.org/honeybee.htm
• Ground-dwelling birds, http//www.birdobservers.or
  g.au/ground_birds.htm
• Sumatran tiger, http//www.saczoo.com/3_kids/20_ca
  mouflage/camouflage_disruptive.htm
• Biomimicry, http//www.wordspy.com/words/biomimicr
  y.asp
• Countershading, http//www.shipcamouflage.com/ship
  s2_3_43_countershading.htm
• Translucence, http//www.gla.ac.uk/ibls/DEEB/teg/p
  roject_pages/counter_shading.htm
• Canny Edge Detection, http//homepages.inf.ed.ac.u
  k/rbf/CVonline/LOCAL_COPIES/OWENS/LECT6/node2.html
  
• Optical Camouflage, http//projects.star.t.u-tokyo
  .ac.jp/projects/MEDIA/xv/VRIC2003.pdf
• Multi-Channel Gradient Model, http//www.psychol.u
  cl.ac.uk/pmco/McGM.html