Dtyjlui

I am using Google's PhotScan app to scan all my old photos that are taken before the digital cameras age, and I am saving these photos using the date of the photo (example: 19821011_trip.jpg, yyyymmdd_trip.jpg).

But this method saves the current date of taking the photo using the app in the photo's properties, so what I was trying to write is a script that will take the date information from the photo's filename and correct the date that is stored in the photo's file properties.

Looking forward to get your help.

exiftool to the rescue

I assume you want to change the EXIF data of your scanned images according to the timestamp from the image's filename (not from the time the file was created like e.g. ls -l shows).

Fortunately, there is a handy tool for this called exiftool. If it is not yet installed, run

sudo apt install libimage-exiftool-perl

first. exiftool is in the standard repositories. It can show and manipulate both filenames and EXIF data. For example, it is possible to move files around according to the EXIF attribute CreateDate and move files to subdirectories like

2018

    Jan

       img0001.jpg

       img0002.jpg

    Feb

       img0003.jpg

       img0004.jpg

and so on. But that's another story and you want it just the other way round.

Let's take your 19821011_trip.jpg as an example and set all three attributes DateTimeOriginal, CreateDate, and ModifyDate to Oct 11, 1982. exiftool has a parameter to parse the filename for something that looks like a date and timestamp and then set all these dates at once to that value. Unfortunately the filename must contain a timestamp (HHMMSS) for this to work, like so:

exiftool "-alldates<filename" 19821011_130000_trip.jpg

This would set the three date attributes mentioned above to Oct 11, 1982, 01:00:00 PM. Since your filename does not contain such an HHMMSS part, we must change the parameter a bit:

exiftool '-alldates<${filename;$_=substr($_,0,8)} 13:00:00' 19821011_trip.jpg 

This will pick the first 8 characters from the filename, append 13:00:00 and finally parse that string (19821011 13:00:00) to build a proper date for all three attributes. exiftool is pretty good at parsing timestamps, but it needs at least an HHMM part after the date.

You can also run exiftool on a whole directory:

exiftool '-alldates<${filename;$_=substr($_,0,8)} 13:00:00' .

It will then process all images it finds. No worries, it makes backups of all modified files.

Summary:

me@ubuntu:~> exiftool -alldates 19821011_trip.jpg

(no output)



me@ubuntu:~> exiftool '-alldates<${filename;$_=substr($_,0,8)} 13:00:00' 19821011_trip.jpg 

    1 image files updated



me@ubuntu:~> exiftool -alldates 19821011_trip.jpg 

Date/Time Original              : 1982:10:11 13:00:00

Create Date                     : 1982:10:11 13:00:00

Modify Date                     : 1982:10:11 13:00:00

You could do that with touch and a loop like

for i in *.jpg; do

  touch -d"${i%_trip.jpg}" "$i"

done

but that’s not very exact, as your file names only contain the date without any time information, the file’s time will thus be set to 00:00:00.000000000. Stay with me for a better way.

Every regular photo has an Exif header which contains the correct time stamp of when the photo was taken, provided the date and time settings of the camera were correct. I always prefer using this, it’s failproof and easy with jhead from the package jhead, see man jhead for details. Some useful options are:

-ft    Sets the file's system time stamp to what is stored in the Exif header.    

-n[format_string]

       This option causes files to be renamed and/ or mmoved using the date information from the Exif header "DateTimeOriginal" field.  If the file is not an Exif file, or the DateTimeOriginal

       does not contain a valid value, the file date is used.  If the new name contains a '/', this will be interpreted as a new path, and the file will be moved accordingly.

A command to rename all jpg files in the current directory according to their Exif header time stamp and changing the file's system time stamp could be:

jhead -ft -n'%Y%m%d_trip' *.jpg

jhead is wise enough not to overwrite your files if the filename already exists:

If the target name already exists, the name will be appended with "a",
"b", "c", etc, unless the name ends with a letter, in which case it
will be appended with "0", "1", "2", etc.

If your files don’t have an Exif header the following options may be of help:

-mkexif

       Creates  minimal exif header. Exif header contains date/time, and empty thumbnail fields only. Date/time set to file time by default. Use with -rgt option if you want the exif header to

       contain a thumbnail. Note that exif header creation is very limited at this time, and no other fields can be added to the exif header this way.

-dsft  Sets the Exif timestamp to the file's timestamp. Requires an Exif header to pre-exist. Use -mkexif option to create one if needed.