exif-date-change

#!/usr/bin/env bash
#
# Simple and intuitive bash script that uses exiftool to modify exif
# dates. You would want to use it typically when you took some pictures
# and later on you realized that you hadn't configured the clock of your
# camera properly.
#
# --------------------------------------------------------------------
#
#  Copyright (C) 2018 Vangelis Tasoulas <cyberang3l@gmail.com>
#
#  This program is free software: you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation, either version 3 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
# --------------------------------------------------------------------

which_bin_or_exit () {
	bin="${1}"
	>/dev/null which "${bin}" 2>&1
	if [[ $? -ne 0 ]] ; then
		echo "Could not find binary '${bin}' in your \$PATH."
		echo "Please install (or make it available in \$PATH) ${bin} and try again."
		exit 1
	fi
}

which_bin_or_exit exiftool

usage () {
	echo ""
	echo "$(basename $0) [OPTION]... [IMAGE]..."
	echo ""
	echo "Shifts the Exif date from a list of images."
	echo "Uses the exiftool to achieve that goal."
	echo ""
	echo "Options:"
	echo "  -h, --help             Shows this help message"
	echo "  -d, --dry-run          Shows the time changes for all provided IMAGES without"
	echo "                          applying any changes. Use this for testing."
	echo ""
	echo "  -r R_EXIF_TIME_TAG, --reference-exif-tag R_EXIF_TIME_TAG"
	echo "                         The R_EXIF_TIME_TAG is a valid time tag that can be extracted"
	echo "                          from the photograph with the exiftool. The R_EXIF_TIME_TAG"
	echo "                          is used as a reference when adding/subtracting the STIME."
	echo "                          Tags that will work (unless they have been stripped) are:"
	echo "                             DateTimeOriginal, CreateDate, ModifyDate,"
	echo "                             FileAccessDate, FileModifyDate, FileInodeChangeDate"
	echo ""
	echo "                          Default value: DateTimeOriginal"
	echo ""
	echo "  -s STIME, --shift-time STIME"
	echo "                         The STIME defines the time shift that will be applied to the"
	echo "                          IMAGES. The format is human readable and must be parsable"
	echo "                          by the date command. Some examples:"
	echo "                           1. The leading minus (-) in the following example indicates"
	echo "                              that the time described in the human readable format will"
	echo "                              be subtracted from the DateTimeOriginal Exif info."
	echo "                               \"-1 year -2 months -13 days -1 hour +15 minutes +3 seconds\""
	echo "                           2. The following example will add 383 days and subtract 3846 seconds."
	echo "                               \"+383 days -3846 seconds\""
	echo ""
	echo "  -m, --update-system-modify-time"
	echo "                         If the -m flag is used, the file system modify time will also"
	echo "                          be updated."
	echo "  -f, --force-delete-backups"
	echo "                         Exiftool takes a backup of an image whenever a modification is"
	echo "                          happening. At the end of the execution of this script you are"
	echo "                          asked if you want to keep these backed up images or delete them."
	echo "                          When using the -f flag, the script will force delete the backups"
	echo "                          at the end."
}

IMAGES=()
while [[ $# -gt 0 ]] ; do
	arg="${1}"
	case "${arg}" in
		-h|--help)
			h=1
			break
			;;
		-d|--dry-run)
			d=1
			shift
			;;
		-m|--update-system-modify-time)
			m=1
			shift
			;;
		-f|--force-delete-backups)
			f=1
			shift
			;;
		-s|--shift-time-str)
			STIME="${2}"
			shift 2
			;;
		-r|--reference-exif-tag)
			R_EXIF_TIME_TAG="${2}"
			if [[ \
				$R_EXIF_TIME_TAG != DateTimeOriginal && \
				$R_EXIF_TIME_TAG != CreateDate && \
				$R_EXIF_TIME_TAG != ModifyDate && \
				$R_EXIF_TIME_TAG != FileAccessDate && \
				$R_EXIF_TIME_TAG != FileModifyDate && \
				$R_EXIF_TIME_TAG != FileInodeChangeDate \
				]] ; then
				echo "Not a valid R_EXIF_TIME_TAG"
				echo "  Valid values are:"
				echo "      DateTimeOriginal, CreateDate, ModifyDate,"
				echo "      FileAccessDate, FileModifyDate, FileInodeChangeDate"
				exit 1
			fi
			shift 2
			;;
		--)
			if [[ -z $after_double_dash ]] ; then
				after_double_dash=1
			else
				IMAGES+=("${arg}")
			fi
			shift
			;;
		-*)
			if [[ -z $after_double_dash ]] ; then
				echo "Error: Unknown argument ${arg}"
				exit 1
			else
				IMAGES+=("${arg}")
			fi
			shift
			;;
		*)
			IMAGES+=("${arg}")
			shift
			;;
	esac
done

if [[ ! -z $h ]] ; then
	usage
	exit 0
fi

if [[ ${#IMAGES[@]} -eq 0 ]] ; then
	echo "No images provided as positional arguments."
	echo "Nothing to be done here..."
	exit 1
fi

date_from_exiftool_fmt () {
	exif_date_tag="${1}"
	image="${2}"
	exif_date=$(exiftool -${exif_date_tag} "${image}" | awk -F' : ' '{print $2}')
	if [[ -z $exif_date ]] ; then
		return 1
	fi
	echo "${exif_date}" | sed -r 's/(....).(..).(..) (.*)/\1\/\2\/\3 \4/'
}

date_to_exiftool_fmt () {
	exif_time_fmt="%Y:%m:%d %H:%M:%S"
	date -d "${1}" +"${exif_time_fmt}"
}

change_fs_modify_date () {
	date_orig="${1}"
	image="${2}"
	date_touch_fmt=$(date -d "${date_orig}" +"%Y%m%d%H%M.%S")
	touch -t ${date_touch_fmt} -m "${image}"
}

if [[ -z $R_EXIF_TIME_TAG ]] ; then
	# Set default value for R_EXIF_TIME_TAG
	R_EXIF_TIME_TAG="DateTimeOriginal"
fi

if [[ ! -z $STIME ]] ; then
	# Validate the STIME
	>/dev/null date -d "${STIME}" 2>&1
	if [[ $? -ne 0 ]] ; then
		echo "Invalid STIME. Please ensure that the provided STIME can be parsed"
		echo "by the 'date -d' command".
		exit 1
	fi
else
	STIME="+0 seconds"
fi


parseble_time_fmt="%Y/%m/%d %H:%M:%S"
print_time_fmt="%Y-%m-%d_%H-%M-%S"
changed_images=()
# Parse the images
for image in "${IMAGES[@]}" ; do
	orig_img_date="$(date_from_exiftool_fmt ${R_EXIF_TIME_TAG} "${image}")"
	if [[ $? -ne 0 ]] ; then
		echo "It seems that some of your images do not have a '${R_EXIF_TIME_TAG}' Exif image tag."
		echo "Aborting on ${image}..."
		exit 1
	fi

	dest_img_date=$(date -d "${STIME} ${orig_img_date}" +"${parseble_time_fmt}")

	info_orig_date="$(date -d "${orig_img_date}" +"${print_time_fmt}")"
	info_dest_date="$(date -d "${dest_img_date}" +"${print_time_fmt}")"
	echo "Processing '${image}'"
	echo "  Current image date: ${info_orig_date}"
	echo "      New image date: ${info_dest_date}"

	if [[ -z $d ]] ; then
		# No dry run has been specified, so do the actual work here
		#
		# Convert the dest to the exif format in order to update the exif tags
		dest_exif_img_date=$(date_to_exiftool_fmt "${dest_img_date}")
		exiftool -AllDates="${dest_exif_img_date}" "${image}"

		# Update the file-system modify date if the m flag is used
		if [[ ! -z $m ]] ; then
			change_fs_modify_date "${dest_img_date}" "${image}"
		fi

		if [[ "${info_orig_date}" != "${info_dest_date}" ]] ; then
    		if [[ -z $f ]] ; then
				changed_images+=( "${image}_original" )
			else
				rm -f "${image}_original"
			fi
		fi

	fi
	echo ""
done

if [[ -z $f && ${#changed_images[@]} -gt 0 ]] ; then
	read -r -p 'Do you want to delete the original pictures that have been backed up? (N/y): ' answer
	if [[ "${answer,,}" == "y" ]] ; then
		for backup_img in "${changed_images[@]}" ; do
			rm -f "${backup_img}"
		done
	fi
fi