geom_image_glyph: Add image glyphs on scatter plot

Description

Each point glyph can be an image (png, jpeg, etc) object.

Usage

geom_image_glyph(
  mapping = NULL,
  data = NULL,
  stat = "identity",
  position = "identity",
  ...,
  images,
  imagewidth = 1.2,
  imageheight = 0.9,
  interpolate = TRUE,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE
)

Value

a geom layer

Arguments

mapping

Set of aesthetic mappings created by aes(). If specified and inherit.aes = TRUE (the default), it is combined with the default mapping at the top level of the plot. You must supply mapping if there is no plot mapping.

data

The data to be displayed in this layer. There are three options:

If NULL, the default, the data is inherited from the plot data as specified in the call to ggplot().

A data.frame, or other object, will override the plot data. All objects will be fortified to produce a data frame. See fortify() for which variables will be created.

A function will be called with a single argument, the plot data. The return value must be a data.frame, and will be used as the layer data. A function can be created from a formula (e.g. ~ head(.x, 10)).

stat

The statistical transformation to use on the data for this layer, either as a ggproto Geom subclass or as a string naming the stat stripped of the stat_ prefix (e.g. "count" rather than "stat_count")

position

Position adjustment, either as a string naming the adjustment (e.g. "jitter" to use position_jitter), or the result of a call to a position adjustment function. Use the latter if you need to change the settings of the adjustment.

...

Other arguments passed on to layer(). These are often aesthetics, used to set an aesthetic to a fixed value, like colour = "red" or size = 3. They may also be parameters to the paired geom/stat.

images

a list of images (a raster object, bitmap image). If not provided, a point visual (geom_point()) will be displayed.

imagewidth

Numerical; width of image

imageheight

Numerical; height of image

interpolate

A logical value indicating whether to linearly interpolate the image (the alternative is to use nearest-neighbour interpolation, which gives a more blocky result). See rasterGrob.

na.rm

If FALSE, the default, missing values are removed with a warning. If TRUE, missing values are silently removed.

show.legend

logical. Should this layer be included in the legends? NA, the default, includes if any aesthetics are mapped. FALSE never includes, and TRUE always includes. It can also be a named logical vector to finely select the aesthetics to display.

inherit.aes

If FALSE, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g. borders().

Aesthetics

geom_..._glyph() understands the following aesthetics (required aesthetics are in bold):

x
y
alpha
colour
fill
group
size
linetype
shape
stroke

The size unit is cm

Note that the shape and stroke do not have real meanings unless the essential argument images is missing. If so, a point visual will be displayed with corresponding shape and stroke.

Examples

Run this code

# \donttest{
# image glyph
if(require("png")) {
img_path <- list.files(file.path(find.package(package = 'ggmulti'),
                                 "images"),
                       full.names = TRUE)
Raptors <- png::readPNG(img_path[2L])
Warriors <- png::readPNG(img_path[3L])

pg <- ggplot(data = data.frame(x = 1:2, y = rep(1, 2)),
       mapping = aes(x = x, y = y)) +
  geom_image_glyph(images = list(Raptors,
                                 Warriors),
                   imagewidth = rep(1.2, 2),
                   imageheight = c(0.9, 1.2)) +
  coord_cartesian(xlim = extendrange(c(1,2)))
pg
# query the images (a numerical array)
build <- ggplot2::ggplot_build(pg)
# `imageRaptors` and `imageWarriors` are three dimensional
# arrays (third dimension specifying the plane)
imageRaptors <- build$data[[1]]$images[[1]]
imageWarriors <- build$data[[1]]$images[[2]]

if(require("grid")) {
grid.newpage()
grid.raster(imageRaptors)
grid.newpage()
grid.raster(imageWarriors)
}

# THIS IS SLOW
mercLogo <- png::readPNG(img_path[1L])

p <- ggplot(mapping = aes(x = hp, y = mpg)) +
       geom_point(
         data = mtcars[!grepl("Merc", rownames(mtcars)), ],
         color = "skyblue") +
       geom_image_glyph(
         data = mtcars[grepl("Merc", rownames(mtcars)), ],
         images = mercLogo,
         imagewidth = 1.5
       )
p

}
# }