Posted by admin on June 21, 2009 under Tech Tips | 
I recently needed to organize a large number of old digital photos that had the wrong date embedded in their EXIF tag data. The camera I used many years ago would often lose track of time and would sometimes be set to the wrong year. Applications I now use to organize photos read this data and made my albums difficult to navigate. I came across a Linux command line utility called jhead that allows you to modify this information to whatever you wish, and its easy to use in scripts as well. Installing was easy, because it’s currently in most repositories, including Ubuntu’s.
To read existing EXIF tag data, simply run jhead against an image without any options. As you can see from the example below, my date is set to the year 2022.
jhead image.jpg
File name : image.jpg
File size : 159390 bytes
File date : 2004:01:12 07:35:23
Camera make : Samsung
Camera model : Digimax 200
Date/Time : 2022:02:12 04:04:17
Resolution : 800 x 600
Flash used : Yes
Exposure time: 0.045 s (1/22)
Aperture : f/2.8
To clear all EXIF data from the file, use the -de option. Then recreate the EXIF fields with the -mkexif option, and check the data again. Notice the new Date/Time is set to the timestamp on the file.
jhead -de image.jpg
Modified: image.jpg
jhead -mkexif image.jpg
Modified: image.jpg
jhead image.jpg
File name : image.jpg
File size : 147751 bytes
File date : 2004:01:12 07:35:23
Date/Time : 2004:01:12 07:35:23
Resolution : 800 x 600
To change the entire timestamp manually, use the -ts option. Notice, there is no space between the -ts and the option. I could not trust the month and day, so I simply chaged the date to midnight on January 1, 2003.
jhead -ts2003:01:01-00:00:00 image.jpg
Modified: image.jpg
jhead image.jpg
File name : image.jpg
File size : 147751 bytes
File date : 2004:01:12 07:35:23
Date/Time : 2003:01:01 00:00:00
Resolution : 800 x 600
For many more options, check out the man page or visit the jhead site for more info.
Posted by admin on December 30, 2007 under Tech Tips |
If you need to resize and watermark large number of images, there is an easy way to do so using Linux command line tools and a very basic shell script. The easiest and most straight-forward method you can use is through the use of the ImageMagick toolkit. If you don’t have it installed already, you can download it from their site. Most distributions have binaries already built for you. Ubuntu and Debian users can install ImageMagick from the main repositories.
Install ImageMagick
sudo apt-get install imagemagick
Prepare your working environment
Make a directory to store the watermark image (~/Pictures/watermark) and photos you’re working on (~/Pictures/temp). Copy the watermark image and original photos to their respective directories.
mkdir -p ~/Pictures/temp/
mkdir -p ~/Pictures/watermark/
cp /path/to/watermark.jpg ~/Pictures/watermark/
cp /path/to/original-photos/*.jpg ~/Pictures/temp/
ls -l ~/Pictures/watermark/
-rw-r--r-- 1 gmendoza gmendoza 3311 2007-12-30 17:35 watermark.jpg
ls -l ~/Pictures/temp
-rw-r--r-- 1 gmendoza gmendoza 885788 2007-12-30 17:35 ubuntu1.jpg
-rw-r--r-- 1 gmendoza gmendoza 128922 2007-12-30 17:31 ubuntu2.jpg
Change directories to begin working on your photos.
cd ~/Pictures/temp/
Resizing with “convert”
Let’s say you want to specify a maximum width of 440 pixels (height being adjusted proportionally) in order for you to post the images appropriately within the specifications of your website borders. The syntax would be the following:
convert -resize 440 original-image.jpg new-image.jpg
In this example, we will specify the same name for the output files, which will overwrite the original copies.
convert -resize 440 ubuntu1.jpg ubuntu1.jpg
convert -resize 440 ubuntu2.jpg ubuntu2.jpg
Watermark with “composite”
You will probably want to watermark the images after they have been resized, this way there is no distortion of the watermark, and it is appropriately sized. In this example, we will also set the watermark transparency level to 15%, and overwrite the original file again.
composite -gravity northeast -dissolve 15 ../watermark/watermark.jpg
ubuntu1.jpg ubuntu1.jpg
composite -gravity northeast -dissolve 15 ../watermark/watermark.jpg
ubuntu2.jpg ubuntu2.jpg
Your photos will now have a nice watermark in their upper right hand corners.
Automating the process with a script
You can automate these steps and apply them to a large number of files using a script of course. Feel free to download this one and modify it to your liking.
https://savvyadmin.com/downloads/watermark.sh
#!/bin/bash
WATERMARK="$HOME/Pictures/watermark/watermark.jpg"
echo "*****************************************"
echo "* Image Resize and Watermarking Script *"
echo "* By Gilbert Mendoza - SavvyAdmin.com! *"
echo "*****************************************"
echo " "
for each in ~/Pictures/temp/*{.jpg,.jpeg,.png}
do
echo "Working on "$each" ..."
convert -resize 440 "$each" "$each" >> /dev/null
composite -gravity northeast -dissolve 15.3 $WATERMARK "$each" "$each" >> /dev/null
echo "... Done!"
done
exit 0
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Additional Options
Please check out the ImageMagick website for more information on the many options and features their products have to offer.
http://www.imagemagick.org/script/command-line-processing.php
http://www.imagemagick.org/script/command-line-options.php
http://www.imagemagick.org/Usage
