align: Align templates and images

In debruine/webmorphR: Reproducible Stimuli

Align templates and images

Description

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

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".

Value

list of stimuli with aligned images and/or templates

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)


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")


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

## End(Not run)

debruine/webmorphR documentation built on Aug. 15, 2022, 3:51 p.m.