paul-loedige
68 lines
2.5 KiB
Markdown
68 lines
2.5 KiB
Markdown
+++
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date = '2026-03-10T18:37:42+01:00'
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draft = false
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title = 'Modify Image Timestamp'
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type='post'
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tags = ['Linux', 'Photography']
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+++
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Some cameras don't automatically update their internal clock. This leads to images with "wrong" timestamps.
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Modifying the [file metadata](https://en.wikipedia.org/wiki/Metadata) as well as the [Exif metadata](https://en.wikipedia.org/wiki/Exif) can fix this problem.
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## Modifying the file metadata
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```bash
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touch -m -d "<date>" "<file_name>"
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```
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- `-m` only modify the modification date
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- `-d "<date>"` use `<date>` instead of the current date
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- `<file_name>` name of the file to be modified
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### Example Script for adding an offset
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The following command adds 20 years and 7 months while subtracting 6 days.
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```bash
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#!/bin/bash
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original_mtime=$(stat -c %y "<file_name>")
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new_mtime=$(date -d "$original_mtime +20 years +7 months -6 days" '+%Y-%m-%d %H:%M:%S')
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touch -m -d "$new_mtime" "<file_name>"
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```
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- `stat -c %y "<file_name>"` reads the current modification timestamp from the file
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- `date -d ...` calculates the new date
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## Modifying the Exif metadata
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```bash
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exiftool -P -overwrite_original "-allDates=<date>" "<file_name>"
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```
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- `exiftool` [FOSS](https://en.wikipedia.org/wiki/Free_and_open-source_software) tool for viewing and modifying Exif data ([source](https://exiftool.org/))
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- `-P` to not overwrite the file modification time (file metadata)
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- `allDates=...` modifies the exif metadata dates
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- can be used with operators (i.e. `+=`, `-=`) for offsets
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### Example Script for adding an offset
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The following command adds 20 years and 7 months while subtracting 6 days.
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```bash
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#!/bin/bash
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exiftool -P -overwrite_original "-allDates+=20:7:0 0:0:0" "<file_name>"
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exiftool -P -overwrite_original "-allDates-=0:0:6 0:0:0" "<file_name>"
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```
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## Example Script for Combined Modification
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This script modifies all `.JPG` files in a given directory by adding 20 years and 7 months while subtracting 6 days.
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```bash
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#!/bin/bash
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find "<dir_name>" -type f -iname "*.JPG" -print0 | while IFS= read -r -d '' file; do
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echo "Processing $file"
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#update meta data
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original_mtime=$(stat -c %y "$file")
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new_mtime=$(date -d "$original_mtime +20 years +7 months -6 days" '+%Y-%m-%d %H:%M:%S')
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touch -m -d "$new_mtime" "$file"
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#update exif data
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exiftool -P -overwrite_original "-allDates+=20:7:0 0:0:0" "$file"
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exiftool -P -overwrite_original "-allDates-=0:0:6 0:0:0" "$file"
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done
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echo "DONE!"
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```
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- `<dir_name>` name of the directory to be modified
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