As pointed out in comments, try the jpeg package.
install.packages("jpeg") ## if necessary
library(jpeg)
## get help
library(help = jpeg)
## get more help
?readJPEG
Example, from the help:
# read a sample file (R logo)
img <- readJPEG(system.file("img", "Rlogo.jpg", package="jpeg"))
Another option is rgdal, which can read from a massive bestiary of formats. Plotting and manipulation are handled differently.
install.packages("rgdal") ## if necessary
library(rgdal)
img <- readGDAL(file.path(R.home(), "doc", "html", "logo.jpg"))
There is also the readbitmap package on CRAN, it's always worth a basic search of the packages list for what you are looking for.
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