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Oval face-region mask for a square image

Source: R/face_mask.R
face_mask.Rd

Returns a logical vector of length prod(img_dims) marking an elliptical face region (or sub-region) centred on the image. Pass to diagnose_infoval() (and infoval()) via the mask argument to restrict both observed and reference Frobenius norms to the masked region.

Usage

face_mask(
  img_dims,
  region = c("full", "eyes", "nose", "mouth", "upper_face", "lower_face"),
  centre = c(0.5, 0.5),
  half_width = 0.35,
  half_height = 0.45
)

Arguments

img_dims

Integer c(nrow, ncol), or a single integer for a square image.

region

Character. One of "full" (default), "eyes", "nose", "mouth", "upper_face", "lower_face".

centre

Numeric c(row, col) in (0, 1) image-fraction coordinates. Default c(0.5, 0.5).

half_width

Full-face ellipse horizontal half-axis as a fraction of image width. Default 0.35.

half_height

Full-face ellipse vertical half-axis as a fraction of image height. Default 0.45.

Value

Logical vector of length prod(img_dims), column-major.

Details

Five regions are supported:

  • "full" (default): the full face oval (Schmitz, Rougier, & Yzerbyt 2024 geometry).

  • "eyes": two small ellipses at typical eye positions.

  • "nose": a narrow vertical ellipse along the midline.

  • "mouth": a wide-and-short ellipse below centre.

  • "upper_face", "lower_face": the top and bottom halves of the full face oval.

All region geometries are heuristic approximations matched to a typical centred face on a square base image (e.g., 256x256 KDEF male). For non-default base images, tune centre, half_width, and half_height; the sub-region geometries scale relative to that ellipse.

References

Schmitz, M., Rougier, M., & Yzerbyt, V. (2024). Introducing the brief reverse correlation: an improved tool to assess visual representations. European Journal of Social Psychology. doi:10.1002/ejsp.3100

See also

diagnose_infoval(), infoval().

Examples

full <- face_mask(c(128L, 128L))
mean(full)              # ~0.49 of the image
#> [1] 0.4875488
eyes <- face_mask(c(128L, 128L), region = "eyes")
mean(eyes)              # ~0.02 of the image
#> [1] 0.01538086