R/add_logo.R

In Hutchins-Center/gghutchins: What the Package Does (One Line, Title Case)

add_logo <- function(plot_path, logo_path, logo_position = 'bottom left', logo_scale = 10){

  # Requires magick R Package https://github.com/ropensci/magick

  # Useful error message for logo position
  if (!logo_position %in% c("top right", "top left", "bottom right", "bottom left")) {
    stop("Error Message: Uh oh! Logo Position not recognized\n  Try: logo_positon = 'top left', 'top right', 'bottom left', or 'bottom right'")
  }

  # read in raw images
  plot <- magick::image_read(plot_path)
  logo_raw <- magick::image_read(logo_path)

  # get dimensions of plot for scaling
  plot_height <- magick::image_info(plot)$height
  plot_width <- magick::image_info(plot)$width

  # default scale to 1/10th width of plot
  # Can change with logo_scale
  logo <- magick::image_scale(logo_raw, as.character(plot_width/logo_scale))

  # Get width of logo
  logo_width <- magick::image_info(logo)$width
  logo_height <- magick::image_info(logo)$height

  # Set position of logo
  # Position starts at 0,0 at top left
  # Using 0.01 for 1% - aesthetic padding

  if (logo_position == "top right") {
    x_pos = plot_width - logo_width - 0.01 * plot_width
    y_pos = 0.01 * plot_height
  } else if (logo_position == "top left") {
    x_pos = 0.01 * plot_width
    y_pos = 0.01 * plot_height
  } else if (logo_position == "bottom right") {
    x_pos = plot_width - logo_width - 0.01 * plot_width
    y_pos = plot_height - logo_height - 0.01 * plot_height
  } else if (logo_position == "bottom left") {
    x_pos = 0.01 * plot_width
    y_pos = plot_height - logo_height - 0.01 * plot_height
  }

  # Compose the actual overlay
  magick::image_composite(plot, logo, offset = paste0("+", x_pos, "+", y_pos))

}