10 Canny Detector Optimal Edge Detector Multiple Stage Algorithm Perform Gaussian smoothingFind edge strengths|G| = |Gx| + |Gy|Detection of edge directiontheta = invtan(Gy/Gx)Relate edge direction toa direction that can be tracedin an imageApply non-maximumsuppressionUse hysteresis to eliminate streaking
11 LaPlacian or LoG Smooth with a Gaussian mask Calculate the second derivativesSearch for zero crossingsOrConvolve the image with theLaplacian of the Gaussian
12 Contrast Energy (CE) Model Uses the output signal from similarly-orientedodd o[x] and even e[x] filters.Energy function is defined as:E2(x) = e2(x) + o2(x)Always positiveShows high output when o(x), e(x) or both are high.
13 Camouflage Detection Methods to be Discussed Convexity-Based Detection – exploits the principle of countershading to detect camouflaged objectsTexture 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 perceivedAs a unit and stands out against the staticbackground
15 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 derivativesThe more derivatives used lowers the chance of that all will be zero at the same timeUses a least sqaures approximation of the derivatives
17 Motion Energy ModelUses 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 detectionAnimals 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.