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 |