LOMAR (version 0.5.0)

circle_hough_transform: Circle Hough transform

Description

Extract coordinates of the centres of circles from a 2D image using the Hough transform

Usage

circle_hough_transform(
  pixels,
  rmin,
  rmax,
  threshold,
  resolution = 360,
  min.separation = rmin/4,
  ncpu = 1
)

Value

a data frame with columns x, y, r and score

Arguments

pixels

input data, either a matrix representing a 2D image or a data frame of signal coordinates with columns x, y. For images, background is expected to be 0 and signal to have positive values.

rmin

minimum search radius.

rmax

maximum search radius.

threshold

score threshold between 0 and 1.

resolution

number of steps in the circle transform (default: 360). This represents the maximum number of votes a point can get.

min.separation

distance between circle centres below which overlapping circles are considered the same and merged (default to 0.25*rmin)

ncpu

number of threads to use to speed up computation (default: 1)

Examples

point.set <- data.frame(x = c(-9.8,-5.2,12.5,2.5,4.5,1.3,-0.2,0.4,9.3,-1.4,0.5,-1.1,-7.7),
                        y = c(-4.2,1.5,-0.5,12,-3,-7.2,10.9,6.7,-1.3,10,6.7,-6.2,2.9))
circles <- circle_hough_transform(pixels = point.set, rmin = 3, rmax = 6, resolution = 100,
                                  threshold = 0.1, ncpu = 1)