demo/rp.image.r

In rpanel: Simple Interactive Controls for R using the 'tcltk' Package

click.capture <- function(panel, x, y) {
  print(x)
  print(y)
  print(panel)
  if (!is.null(panel$x))
    rp.line(panel, "gulls.image", panel$x, panel$y, as.numeric(x), as.numeric(y),
            color="red", width=3, id = "current")
  panel$x <- x
  panel$y <- y
  panel
}

gulls.panel <- rp.control()
image.file <- file.path(system.file(package = "rpanel"), "images", "gulllmks.gif")
gulls.image <- rp.image(gulls.panel, image.file, name = "gulls.image",
                        action = click.capture, pos = list(row=0, column=0))
rp.button(gulls.panel, function(panel) {
   rp.clearlines(gulls.panel, "gulls.image")
   panel}, "Remove lines", pos = list(row = 1, column = 0))