How to recursively resize images from one folder to another? - bash

Question

I would like to create thumbnails of images I have organised into a set of nested subdirectories into a mirror of the file structure so that a command of the type:
./imageresize.sh Large Small 10
...would convert any .jpg or .JPG files, in the directories nested under "./Large":
./Large/Holidays/001.jpg
./Large/Holidays/002.jpg
./Large/Holidays/003.jpg
./Large/Pets/Dog/001.jpg
./Large/Pets/Dog/002.jpg
./Large/Pets/Cat/001.jpg
into thumbnails of 10% to a mirror destination with a different top directory ("Small" instead of "Large" in this e.g.):
./Small/Holidays/001.jpg
./Small/Holidays/002.jpg
./Small/Holidays/003.jpg
./Small/Pets/Dog/001.jpg
./Small/Pets/Dog/002.jpg
./Small/Pets/Cat/001.jpg
This is what I have so far, but I can't seem to get it working. The $newfile variable seems invalid but I don't know why, and when testing, it outputs the result of the 'convert' command to the screen. Any help/suggestions greatly appreciated.
#!/bin/bash
#manage whitespace and escape characters
OIFS="$IFS"
IFS=$'\n'
#create file list
filelist=$(find ./$1/ -name "*.jpg" -o -name "*.JPG")
for file in $filelist
do
#create destination path for 'convert' command
newfile= ${file/$1/$2}
convert "$file" -define jpeg:extent=10kb -scale $3% "$newfile"
done

Answer 1

Don't know if it's just a copy/paste error or if it's actually in your script, but this line:
newfile= ${file/$1/$2}
would be an invalid assignment in Bash as spaces around = isn't allowed when assigning.
Try this instead:
newfile=${file/$1/$2}
As a side-note. find has a case-insensitive search too, -iname, so you could do:
filelist=$(find ./$1/ -iname "*.jpg")
It also has -exec for executing commands on the result set. It's explained very well here: https://unix.stackexchange.com/questions/12902/how-to-run-find-exec So you may be able to do it in one single find. (Note: That's not necessarily better, in most cases it's just a matter of preference, I just mention it as a possibility.)

Answer 2

So - revised working script with corrections suggested by madsen and 4ae1e1 (thanks both), and with rsync commands to create directory structure first, (then clean extraneous files from the destination) :). I've added an extra parameter and parameter checker so that now you can specify source, destination, approx destination file size in kb and percentage of original. Hope it helps someone else. :)
#!/bin/bash
#manage whitespace and escape characters
OIFS="$IFS"
IFS=$'\n'
#check parameters
if [ $# -lt 4 ] || [ "$1" = "--help" ]
then # if no parameters or '--help' as $1 - show help
echo "______________________________________________________________"
echo ""
echo "Useage: thumbnailmirror [Source] [Destination] [Filesize] [Percentage]"
echo "Source - e.g. 'Fullsize' (directory must exist)"
echo "Destination - e.g. 'Thumnail' (directory must exist)"
echo "Filesize - approx filesize in kb e.g. '10'"
echo "Percentage - % of reduction (1-100)"
echo "e.g. thumbnailmirror Fullsize Thumnail 18 7"
echo "______________________________________________________________"
else # parameters exist
#syncronise directory structure (directories only)
rsync -a --include '*/' --exclude '*' ./$1/ ./$2/
# delete any extraneous files and directories at destination
rsync -a --delete --existing --ignore-existing ./$1/ ./$2/
#create file list ( -iname means not case sensitive)
filelist=$(find ./$1/ -iname "*.jpg")
for file in $filelist
do
#define destination filename for 'convert' command
newfile=${file/$1/$2}
if [ ! -f "$newfile" ] #if file doesn't exists create it
then
convert "$file" -define jpeg:extent=$3kb -quality 100 -scale $4% "$newfile"
echo "$file resized"
else #skip it
echo "Skipping $file - exists already"
fi
done
fi