Preparing images for the web
23 Nov 2017Preparing images from your camera or smartphone for using them in a weblog or somewhere else on the web can be a mess.
Since I am not much into reworking the images I like to use automated procedures,
and therefore tend to use the command-line as much as possible.
All the tools mentioned in this post here can be installed using the typical
package managers of your system (e.g. brew for macOS or
apt/aptitude for Debian).
Here are my typical steps for recurring tasks:
resizing images
Tool of choice is convert from the ImageMagick tools.
% find . -name '*.jpg' -exec convert {} -resize 1200x1200 -quality 80 -auto-orient {} \;
Make sure to use auto-orient especially if you took your photos with an iPhone!
Attention: this overwrites your original images, so make sure you are working on copies!
macOS
MacOS ships his own tool for such tasks: sips. It is working in a similar way, but the
generated images are way larger and look worse…
% find -name '*.jpg' -exec sips -Z 1000 {} --out {} \;
graphical
The macOS Preview application offers a build-in batch resizer:
- mark all images
- open in Preview (Apple+O)
- select all thumbnails (with same orientation) in sidebar
- select Tools –> Adjust Size
- now you can select either width or height (thats why you only selected thumbnails with same orientation)
- the file sizes with this method are also worse than with ImageMagick
removing EXIF data
To remove EXIF-data (interesting stuff such as shutter speed, aperture but also
scary stuff like GPS, exact date and time of creation, Camera serial number)
we use the tool exiftool (what a appropriate name).
To remove all EXIF data of all jpg files in your folder just do:
% exiftool -all= -overwrite_original *.jpg
If you are using an iPhone, make sure to -auto-orient the image (see above) before
removing the EXIF-data.
renaming many files in one go
exiftool can also be used to rename files based on EXIF-data.
This can be helpful for renaming from the format of e.g. Canon-cameras (IMG_1234.jpg)
to a more readable format containing date and time (IMG_20171123_164901.jpg):
% exiftool -P '-filename<CreateDate' -d IMG_%Y%m%d_%H%M%S%%-c.%%le *
For more generic renaming most OS/file-managers offer more or less good
solutions, I really like rangers :bulkrename command.
deleting redundant folders and files
When you are switching from any previous CMS or page-builder it can be handy to be able to delete all subdirectories and files of a given directory (e.g. autogenerated thumbnails).
% find . -mindepth 2 -type d -exec rm -r {} \;