R/plot_image.R

In rayimage: Image Processing for Simulated Cameras

#'@title Plot Image
#'
#'@description Displays the image in the current device.
#'
#'@param image Image array or filename of an image to be plotted.
#'@param rotate Default 0. Rotates the output. Possible values: 0, 90, 180, 270.
#'@param draw_grid Default `FALSE`. If `TRUE`, this will draw a grid in the background to help
#'disambiguate the actual image from the device (helpful if the image background is the same as the
#'device's background).
#'@param asp Default `1`. Aspect ratio of the pixels in the plot. For example, an aspect ratio of `4/3` will
#'slightly widen the image.
#'@param new_page  Default `TRUE`. Whether to call `grid::grid.newpage()` before plotting the image.
#'@param return_grob Default `FALSE`. Whether to return the grob object.
#'@export
#'@examples
#'#if(interactive()){
#'#Plot the dragon array
#'plot_image(dragon)
#'#Make pixels twice as wide as tall
#'plot_image(dragon, asp = 2)
#'#Plot non-square images
#'plot_image(dragon[1:100,,])
#'#Make pixels twice as tall as wide
#'plot_image(dragon[1:100,,], asp = 1/2)
#'#end}
plot_image = function(image, rotate=0, draw_grid = FALSE,
                      asp = 1, new_page = TRUE, return_grob = FALSE) {
  image = ray_read_image(image) #Always output RGB array
  if(dim(image)[3] == 4) {
    if(any(image[,,4] != 1)) {
      message("Note: alpha channel will be ignored when plotting image.")
    }
  }
  rotatef = function(x) t(apply(x, 2, rev))
  if(!(rotate %in% c(0,90,180,270))) {
    if(length(rotate) == 1) {
      warning(paste0("Rotation value ",rotate," not in c(0,90,180,270). Ignoring"))
    } else {
      warning(paste0("Rotation argument `rotate` not in c(0,90,180,270). Ignoring"))
    }
    number_of_rots = 0
  } else {
    number_of_rots = rotate/90
  }

  if(number_of_rots != 0) {
    newarray = image
    newarrayt = array(0,dim=c(ncol(image),nrow(image),3))
    for(i in seq_len(number_of_rots)) {
      for(j in 1:3) {
        if(i == 2) {
          newarray[,,j] = rotatef(newarrayt[,,j])
        } else {
          newarrayt[,,j] = rotatef(newarray[,,j])
        }
      }
    }
    if(number_of_rots == 2) {
      image = newarray
    } else {
      image = newarrayt
    }
  }
  if(any(image > 1 | image < 0,na.rm = TRUE)) {
    image[image > 1] = 1
    image[image < 0] = 0
  }
  nr = convert_to_native_raster(image)

  if(new_page) {
    grid::grid.newpage()
  }

  # Draw a grid to differentiate image from background
  if(draw_grid) {
    draw_grid_fxn = function() {
      grid::pushViewport(
        grid::viewport(layout = grid::grid.layout(1, 1,
                                                  widths = grid::unit(1, "npc"),
                                                  heights = grid::unit(1, "npc")))
      )
      # Define grid density and angle
      grid_density = 0.01 # Adjust this value for tighter or looser grid
      for (i in seq(-2, 2, by = grid_density)) {
        grid::grid.lines(x = c(0, 1), y = c(i, i + 1), default.units = "npc", gp = grid::gpar(col = "grey"))
        grid::grid.lines(x = c(0, 1), y = c(i, i - 1), default.units = "npc", gp = grid::gpar(col = "grey"))
      }
      grid::popViewport()
    }
    draw_grid_fxn()
  }
  return(plot_asp_native_raster(nr, asp = asp, return_grob = return_grob))
}