Converting bytea hex data to binary for jpg

I have extracted hex data from a postgres bytea column. The data which was inserted was from a JPG image. I have use the followed code to extract the data and write it to a jpg file.


# get the data from the database
rc <- odbcConnect('odk_prod')
img_tbl <- sqlQuery(rc, 'select * from odk_prod."GRAVEL_ROADS_1_3_GRAVEL_PHOTO_BLB"')

# create the file for writing and squirt the 1's and 0's in it
to.write = file("img.jpg","wb")
writeBin( (unlist(img_tbl[1,'VALUE'])), to.write)

but when the jpg file is opened it is "corrupted". I assume I need to encode the output in a binary format. In this post: Storing and retrieving files/images in a database from Shiny app, someone is doing the same process, but they get out what they put in.

I am guessing I need to encode the hex data into binary data, but don't know how to do that in R.
Any function tips? or code tips would be great!

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