Plot image from BLOB/RAW

Question

I'm trying to use the ROracle package to pull images from a database. The images are stored in the database as BLOBs.

I've managed to get the images into R in "raw" format. Is there a way to convert it from raw into jpeg/png?

This is what I have so far:

con <- dbConnect(drv, username = user,
                 password = pw, dbname=connect.string)

query.string <- paste("select db.img",
                      "from database db",
                      "where db.id = '01234567')")

## run a SQL statement by first creating a resultSet object
rs <- dbSendQuery(con, query.string)
## fetch records from the resultSet into a data.frame
data <- fetch(rs)
## extract all rows
str(data)

> str(data)
'data.frame':   1 obs. of  1 variable:
 $ DATA:List of 1
  ..$ : raw  ff d8 ff e1 ...

Ideally, I could then do something like this:

pic <- rawToJpeg(unlist(data)[1])

which would then allow me to plot/save the image

score 1 · Accepted Answer · answered Mar 27 '19 at 17:31

1

Consider using writeBin to transfer the binary data to file:

rawToJpeg <- function(pic_data) {
    f = file(paste0('output.jpeg'), "wb")           # OPEN FILE CONNECTION
    writeBin(pic_data, con = f, useBytes=TRUE)      # TRANSFER RAW DATA
    close(f)                                        # CLOSE FILE CONNECTION
}

rawToJpeg(unlist(data)[1])

answered Mar 27 '19 at 17:31

Parfait

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Great to hear! Using `odbc` on an Oracle database, I never could get the blob out without conversion to `hex` first than to `raw`. Maybe `ROracle` does it different. – Parfait Mar 27 '19 at 20:21

Plot image from BLOB/RAW

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