geom_multi_raster: Geom Layer for Drawing Multiple Rasters
In plothelper: New Plots Based on 'ggplot2' and Functions to Create Regular Shapes

Unlike annotation_raster which draws only 1 raster, this layer draws one or more rasters at the same time. The data must be a tbl object created by package tibble and the reason is that, as we must give each rectangle a vector of colors, the column that contains these vectors of colors must be a list rather than a vector. A list can be a column for tbl object, not for a normal data frame. See examples. Accepted properties are:

(1) xmin.
(2) xmax.
(3) ymin.
(4) ymax.
(5) raster. a list with 1 or more rasters. If you have only 1 raster, you also have to put it into a list. Each raster should be a matrix, a raster object, a character vector or a magick object read into R by magick::image_read. You can also use a data frame created by package tibble to combine xmin, xmax, ymin, ymax, raster.
(6) interpolate. It is the same as that in annotation_raster except that the default value is TRUE. It can be used either inside or outside the aes(...) function. Its length must be either 1 or the same as the number of rasters.
(7) flip. The default is FALSE. You only need to use TRUE when you use coord_flip. Used outside the aes(...) function.

geom_multi_raster(
  mapping = NULL,
  data = NULL,
  stat = "identity",
  position = "identity",
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE,
  flip = FALSE,
  ...
)

`mapping`	aes mapping.
`data`	data. It should be a tbl object.
`stat`	stat.
`position`	position.
`na.rm`	logical, whether to remove NA values.
`show.legend`	This will not be used because the layer does not create any legend.
`inherit.aes`	logical, whether to inherit aes from ggplot().
`flip`	see description.
`...`	additional parameters.

# Example 1: use vectors and a list. 
mycolor=list(
	c1=matrix(c("red", "blue", "green", "yellow"), nrow=2), 
	c2=matrix(c("green", "yellow")), 
	c3=matrix(c("purple", "red")))
xmin=1: 3
xmax=(1: 3)+0.8 
ymin=c(0, 1, 2)
ymax=c(1, 3, 5)
ggplot()+
	geom_multi_raster(aes(xmin=xmin, xmax=xmax, 
	ymin=ymin, ymax=ymax, raster=mycolor))
#
# Example 2: the same as example 1
# except flip=TRUE.
ggplot()+coord_flip()+
	geom_multi_raster(aes(xmin=xmin, xmax=xmax, 
	ymin=ymin, ymax=ymax, raster=mycolor), flip=TRUE)