Skip to contents

Align templates and images

Source: R/align.R
align.Rd

Align images so that template points line up. Defaults to two-point alignment of the first two points in your template (usually the eyes) to their mean coordinate position across the stimuli.

Usage

align(
  stimuli,
  pt1 = 0,
  pt2 = 1,
  x1 = NULL,
  y1 = NULL,
  x2 = NULL,
  y2 = NULL,
  width = NULL,
  height = NULL,
  ref_img = NULL,
  fill = wm_opts("fill"),
  procrustes = FALSE
)

Arguments

stimuli

list of stimuli

pt1

The first point to align (defaults to 0)

pt2

The second point to align (defaults to 1)

x1, y1, x2, y2

The coordinates to align the first and second point to

width, height

The dimensions of the aligned images

ref_img

The reference image to get coordinates and dimensions from if they are NULL

fill

background color if cropping goes outside the original image, see color_conv()

procrustes

logical; whether to use procrustes alignment

Value

list of stimuli with aligned images and/or templates

Details

Setting pt1 the same as pt2 aligns 1 point, but does not resize or rotate images. Setting pt1 and pt2 aligns 2 points, resizing and rotating faces. Setting procrustes = TRUE uses Procrustes analysis to resize and rotate images to be as close as possible to a mean shape.

You can specify the x and y coordinates to align, and the width and height of the output images, or set them from a reference image. The reference image (ref_img) can be a stim, a 1-item stimlist, or the index or name of a stim in stimuli. It defaults to average of all stimuli if NULL.

Visualise the template points with draw_tem() to determine which to align, using pt.shape = "index".

See also

Stimulus manipulation functions crop_tem(), crop(), greyscale(), horiz_eyes(), image_func(), mask_oval(), mask(), mirror(), pad(), resize(), rotate(), to_size()

Examples

# align eye points to specific x and y coordinates
# in a 300x300 pixel image
demo_unstandard(1:3) |>
  align(pt1 = 0, pt2 = 1,
        x1 = 100, x2 = 200, y1 = 100, y2 = 100, 
        width = 300, height = 300)


# \donttest{
orig <- demo_unstandard()

# align to bottom-centre of nose (average position)
align(orig, pt1 = 55, pt2 = 55, fill = "dodgerblue")


# align to pupils of second image
align(orig, ref_img = 2, fill = "dodgerblue")

# }

if (FALSE) {
# procrustes align to average position
# this requires XQuartz on mac and may not run on linux
align(orig, procrustes = TRUE, fill = "dodgerblue")
}