Batch converting PNG to JPG with convert from the ImageMagick suite

[melodie]

Hi,

All is here:
http://superuser.com/questions/71028/batch-converting-png-to-jpg-in-linux

10 down vote

The convert command found on many Linux distributions is installed as part of the ImageMagick suite. Here's the bash code to run convert on all PNG files in a directory and avoid that double extension problem:

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for img in *.png; do
    filename=${img%.*}
    convert "$filename.png" "$filename.jpg"
done

This is the one I just used, I ended with both png and jpg files in the same directory, which was the perfect result.

I have a couple more solutions.

The simplest solution is like most already posted. A simple bash for loop.

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for i in *.png ; do convert "$i" "${i%.*}.jpg" ; done
For some reason I tend to avoid loops in bash so here is a more unixy xargs approach, using bash for the name-mangling.

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ls -1 *.png | xargs -n 1 bash -c 'convert "$0" "${0%.*}.jpg"'
The one I use. It uses GNU Parallel to run multiple jobs at once, giving you a performance boost. It is installed by default on many systems and is almost definitely in your repo (it is a good program to have around).

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ls -1 *.png | parallel convert '{}' '{.}.jpg'
The number of jobs defaults to the number of processes you have. I found better CPU usage using 3 jobs on my dual-core system.

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ls -1 *.png | parallel -j 3 convert '{}' '{.}.jpg'
And if you want some stats (an ETA, jobs completed, average time per job...)

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ls -1 *.png | parallel --eta convert '{}' '{.}.jpg'
There is also an alternative syntax if you are using GNU Parallel.

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parallel convert '{}' '{.}.jpg' ::: *.png
And a similar syntax for some other versions (including debian).

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parallel convert '{}' '{.}.jpg' -- *.png

More on the above linked page.