R/ending.R

In tkatsuki/dipr: Digital Image Processing with R

#' Detection of end points in a skeletonized image
#'
#' @param x skeletonized image
#' @export
#' @examples
#' ending()

ending <- function(x) {

  # prepare lookup tables
  h1 <- c(0, 1, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0,
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0,
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0,
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)

  # define stacking function
  stacking <- function(img){
    r <- 1
    row <- nrow(img)
    col <- ncol(img)

    img <- rbind(matrix(0, r, col+2*r),
                 cbind(matrix(0, row, r), img, matrix(0, row, r)),
                 matrix(0, r, col+2*r))

    stack <- array(c(img[1:row, 2:(col+1)]*2^7,
                     img[1:row, 3:(col+2)]*2^6,
                     img[2:(row+1), 3:(col+2)]*2^5,
                     img[3:(row+2), 3:(col+2)]*2^4,
                     img[3:(row+2), 2:(col+1)]*2^3,
                     img[3:(row+2), 1:col]*2^2,
                     img[2:(row+1), 1:col]*2^1,
                     img[1:row, 1:col]*2^0),
                   c(row, col, 8))
    stack
    }

  stack1 <- stacking(x)

  # convert stack to 8 bit integer values
  key1 <- rowSums(stack1, dim=2)

  # apply lookup table
  flag1 <- matrix(h1[key1+1], nrow(key1), ncol(key1))
  x1 <- x*flag1
  x1
}