simulate_cvd {colorspace}

Simulate Color Vision Deficiency

Description

Transformation of R colors by simulating color vision deficiencies, based on a CVD transform matrix.

Usage

simulate_cvd(col, cvd_transform, linear = TRUE)

deutan(col, severity = 1, linear = TRUE)

protan(col, severity = 1, linear = TRUE)

tritan(col, severity = 1, linear = TRUE)

interpolate_cvd_transform(cvd, severity = 1)

Arguments

col

vector of R colors. Can be any of the three kinds of R colors, i.e., either a color name (an element of colors), a hexadecimal (hex) string of the form "#rrggbb" or "#rrggbbaa" (see rgb), or an integer i meaning palette()[i]. Additionally, col can be a formal color-class object or a matrix with three named rows (or columns) containing R/G/B (0-255) values.

cvd_transform

numeric 3x3 matrix, specifying the color vision deficiency transform matrix.

linear

logical. Should the color vision deficiency transformation be applied to the linearized RGB coordinates (default)? If FALSE, the transformation is applied to the gamma-corrected sRGB coordinates (which was the default up to version 2.0-3 of the package).

severity

numeric. Severity of the color vision defect, a number between 0 and 1.

cvd

list of cvd transformation matrices. See cvd for available options.

Details

Using the physiologically-based model for simulating color vision deficiency (CVD) of Machado et al. (2009), different kinds of limitations can be emulated: deuteranope (green cone cells defective), protanope (red cone cells defective), and tritanope (blue cone cells defective). The workhorse function to do so is simulate_cvd which can take any vector of valid R colors and transform them according to a certain CVD transformation matrix (see cvd) and transformation equation.

The functions deutan, protan, and tritan are the high-level functions for simulating the corresponding kind of colorblindness with a given severity. Internally, they all call simulate_cvd along with a (possibly interpolated) version of the matrices from cvd. Matrix interpolation can be carried out with the function interpolate_cvd_transform (see examples).

If input col is a matrix with three rows named R, G, and B (top down) they are interpreted as Red-Green-Blue values within the range [0-255]. Then the CVD transformation is applied directly to these coordinates avoiding any further conversions.

Finally, if col is a formal color-class object, then its coordinates are transformed to (s)RGB coordinates, as described above, and returned as a formal object of the same class after the color vision deficiency simulation.

Up to version 2.0-3 of the package, the CVD transformations had been applied directly to the gamma-corrected sRGB coordinates (corresponding to the hex coordinates of the colors), following the illustrations of Machado et al. (2009). However, the paper implicitly relies on a linear RGB space (see page 1294, column 1) where their linear matrix transformations for simulating color vision deficiencies are applied. Therefore, starting from version 2.1-0 of the package, a new argument linear = TRUE has been added that first maps the provided colors to linearized RGB coordinates, applies the color vision deficiency transformation, and then maps back to gamma-corrected sRGB coordinates. Optionally, linear = FALSE can be used to restore the behavior from previous versions. For most colors the difference between the two strategies is negligible but for some highly-saturated colors it becomes more noticable, e.g., for red, purple, or orange.

Value

A color object as specified in the input col (hexadecimal string, RGB matrix, or formal color class) with simulated color vision deficiency.

References

Machado GM, Oliveira MM, Fernandes LAF (2009). “A Physiologically-Based Model for Simulation of Color Vision Deficiency.” IEEE Transactions on Visualization and Computer Graphics. 15(6), 1291–1298. doi:10.1109/TVCG.2009.113 Online version with supplements at http://www.inf.ufrgs.br/~oliveira/pubs_files/CVD_Simulation/CVD_Simulation.html.

Zeileis A, Fisher JC, Hornik K, Ihaka R, McWhite CD, Murrell P, Stauffer R, Wilke CO (2020). “colorspace: A Toolbox for Manipulating and Assessing Colors and Palettes.” Journal of Statistical Software, 96(1), 1–49. doi:10.18637/jss.v096.i01

See Also

cvd

Examples

# simulate color-vision deficiency by calling `simulate_cvd` with specified matrix
simulate_cvd(c("#005000", "blue", "#00BB00"), tritanomaly_cvd["6"][[1]])

# simulate color-vision deficiency by calling the shortcut high-level function
tritan(c("#005000", "blue", "#00BB00"), severity = 0.6)

# simulate color-vision deficiency by calling `simulate_cvd` with interpolated cvd matrix
simulate_cvd(c("#005000", "blue", "#00BB00"),
             interpolate_cvd_transform(tritanomaly_cvd, severity = 0.6))

# apply CVD directly on wide RGB matrix (with R/G/B channels in rows)
RGB <- diag(3) * 255
rownames(RGB) <- c("R", "G", "B")
deutan(RGB)