Imagemagick Convert on a Multiple Files
I Have 3 Files in a Directory: Aaa. Jpg Bbb. Jpg Ccc. Jpg I Can Scale Down an Image Using Imagkmagick Convert: Convert Aaa. Jpg -Resize 1200X900 Aaa-Small. Jpg...
I have 3 files in a directory:
aaa.jpg
bbb.jpg
ccc.jpg
I can scale down an image using ImagkMagick convert:
convert aaa.jpg -resize 1200x900 aaa-small.jpg
I want to do all the images in the directory, something like:
convert *.jpg -resize 1200x900 *-small.jpg
but this results in files named like so:
*-small-0.jpg
*-small-1.jpg
*-small-2.jpg
What I want is:
aaa-small.jpg
bbb-small.jpg
ccc-small.jpg
How do I do this?
3 Answers
It's frustratingly opaque in the documentation, but you can pass a quoted shell glob to convert (quoted to prevent the shell from expanding it prematurely), and use Filename Percent Escapes to construct output filenames in the form %[filename:label] (where label is an arbitrary user-specified label), using the input basename escape %[basename] or its legacy equivalent %t:
$ ls ???.jpg
aaa.jpg bbb.jpg ccc.jpg
then
$ convert '*.jpg' -set filename:fn '%[basename]-small' -resize 1200x900 '%[filename:fn].jpg'
resulting in
$ ls ???-small.jpg
aaa-small.jpg bbb-small.jpg ccc-small.jpg
In a for loop it is possible to use the features described in man bash at
Parameter Expansion
...
${parameter%word}
${parameter%%word}
Remove matching suffix pattern. The word is expanded to produce a pattern just
as in pathname expansion. If the pattern matches a trailing portion of the
expanded value of parameter, then the result of the expansion is the expanded
value of parameter with the shortest matching pattern (the ``%'' case) or the
longest matching pattern (the ``%%'' case) deleted. If parameter is @ or *,
the pattern removal operation is applied to each positional parameter in turn,
and the expansion is the resultant list. If parameter is an array variable
subscripted with @ or *, the pattern removal operation is applied to each member
of the array in turn, and the expansion is the resultant list.
The following one-liner should do the job
for f in ./*.jpg ; do convert "$f" -resize 1200x900 "${f%.jpg}-small.jpg" ; done
This works in bash, which is the standard shell of Ubuntu. I think it is easier to remember than the elegant method by Steeldriver (who uses only convert and no for construct).
mkdir small
for f in *.jpg ; do convert $f -resize 1200x900 small/$f ; done
Marcus Vance is a cybersecurity auditor and technology writer dedicated to educating the public about online safety, data privacy regulations, enterprise security, and emerging cyber threats.
