Add png to {ggplot2} that has transparent background and was rotated via {magick}

Question

While adding a transparent png to a ggplot works fine via ggplot2::annotation_custom() (but not via patchwork::inset_element), there seem to be problems when rotating the image via magick::image_rotate().

Find the reprex below. Does anyone have a solution for this?

^{NOTE: While there is some overlap, I do not consider this question to be a duplicate of R/ggplot2: Add png with transparency info or Transparent background graph with ggplot2 in high resolution, R, since the problem here seems to specifically arise due to the image rotation.}

library(magick)
library(patchwork)
library(tidyverse)

url <- "https://upload.wikimedia.org/wikipedia/commons/thumb/d/d0/RStudio_logo_flat.svg/2560px-RStudio_logo_flat.svg.png"

img <- magick::image_read(url) %>%
  grid::rasterGrob()

img_rot <- magick::image_read(url) %>%
  magick::image_rotate(30) %>% 
  grid::rasterGrob()

ggplot(tibble(x = 1:3)) +
  aes(x = x, y = x) +
  geom_point() +
  coord_fixed() +
  ggplot2::annotation_custom(img, 1, 2, 2, 3) +
  ggplot2::annotation_custom(img_rot, 2, 3, 2, 3) +
  patchwork::inset_element(img,     0, 0, 0.5, 0.5) +
  patchwork::inset_element(img_rot, 0.5, 0, 1, 0.5)

^{Created on 2022-08-26 with reprex v2.0.2}

score 3 · Accepted Answer · answered Aug 26 '22 at 14:19

This doesn't really have anything to do with ggplot specifically. The rotate changes the size of the image but does not set the background transparent. The image will always have a rectangular shape. You need to set the background so magick knows what to fill in the newly created space with

img_rot <- magick::image_read(url) %>%
  magick::image_background("none") %>% 
  magick::image_rotate(30) %>% 
  grid::rasterGrob()

Add png to {ggplot2} that has transparent background and was rotated via {magick}

1 Answers1