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Table 1 Descriptions of the methods used to measure prey conspicuousness

From: Quantifying camouflage: how to predict detectability from appearance

Camouflage Category Variable Name Filtering Method Basic Description
Edge Disruption GabRat Gabor Filter Average ratio of ‘false edges’ (edges at right angles to the prey outline) to ‘salient edges’ (edges parallel with the prey outline). See Additional file 1
VisRat Canny Edge Detector Proportion of Canny edge pixels in the prey’s outline region [21]
DisRat Canny Edge Detector Proportion of Canny edge pixels in the prey’s outline region [34]
Mean Edge-region Canny Edges Canny Edge Detector Proportion of Canny edge pixels in the prey’s outline region.
Edge-intersecting cluster count None Count of the number of changes in the pattern around the prey’s outline [33]
Pattern/Object detection SIFT Difference-of-Gaussians, Hough Transform Uses Hough transform to find features in the prey, then counts how many similar features are found in the background [19, 22]
HMAX Gabor Filter Breaks down a bank of Gabor Filter outputs into layers that describe patterns with some invariance to scale and orientation [20]
Pattern PatternDiff Fourier Bandpass Sums the absolute difference between the prey’s pattern statistics [42]
Euclidean Pattern Distance Fourier Bandpass Euclidean distance between normalised descriptive pattern statistics [42]
Luminance Mean Backgorund Luminance Luminance Mean luminance
Mean Luminance Difference Luminance Absolute difference between mean prey and mean background luminance
LuminanceDiff Luminance Sum of absolute luminance histogram bins [16]
Contrast Difference Luminance Absolute difference of contrast between prey and background, where contrast is the standard deviation in luminance levels