R/stepEdgeLL2K.r

In DRIP: Discontinuous Regression and Image Processing

# This is R source code for function 'stepEdgeLL2K', in the R
# package "image".
# Date: April 29, 2013
# Creator: Yicheng Kang

stepEdgeLL2K <- function(image, bandwidth, thresh, plot =
                           FALSE){
  if (!is.matrix(image))
    stop("image data must be a matrix")
  n1 <- as.integer(dim(image)[1])
  n2 <- as.integer(dim(image)[2])
  if (n1 != n2)
    stop("image data must be a square matrix")
  if (!is.numeric(bandwidth))
    stop("bandwidth must be numeric")
  if (as.integer(bandwidth) < 1)
    stop("bandwidth must be a positive integer")
#   if (n1 + 2 * bandwidth + 2 > 600)
#     stop("bandwidth is too large or the resolution
# of the image is too high.")
  if (!is.numeric(thresh))
    stop("threshold  must be numeric")
  n1 <- dim(image)[1]
  z <- matrix(as.double(image), ncol = n1)
  k <- as.integer(bandwidth)
  u <- as.double(thresh)
  out <- .Fortran(C_ll2k_diff, n = as.integer(n1 - 1), obsImg = z,
                  bandwidth = as.integer(k), diff = z)
  edge <- out$diff
  edge[out$diff < u] <- 0
  edge[out$diff >= u] <- 1
  if (plot == FALSE) { return(edge) }
  if (plot == TRUE) {
    x <- seq(0, 1, length = n1) 
    y <- x
    image(x, y, 1 - edge, col = gray(0:1))
    return(edge)
  }
}