How to save a ggplot as a JPG file with specific dimensions and a high dpi

ggplot-to-jpg-set-dpi.R

# How to save a ggplot as a JPG file with a 
# specific dpi and dimensions, for example,
# because a publisher requires it

library(ggplot2)

p <-
  ggplot(mtcars) +
  aes(mpg, 
      disp) +
  geom_point()

pngfile <- here::here("plot.png")
jpgfile <- here::here("plot.jpg")
dpi <- 1000

library(ragg)

# write PNG file with desired size and resolution
agg_png(pngfile,
        width = 5,
        height = 5,
        units = "cm",
        res = dpi,
        scaling = 0.75)
p

invisible(dev.off())

# convert PNG to JPG
library(magick)
img_in <- image_read(pngfile)
png_2_jpg <- image_convert(img_in, "jpg")
image_write(png_2_jpg, jpgfile, density = dpi, quality = 100)

# may need to adjust base_size, label_size, aelement_text(size, and other
# text size values to make it look the right size in the JPG