Bash Run Script on Multiple Files

Question

I have a simple bash script running a command in ImageMagick. It takes an image (INFILE - typically a .tif), resizes it, and saves the result (OUTFILE - typically a .jpg)

INFILE=/path/'image name.tif'
OUTFILE=/path/'image name.jpg'

echo INFILE="${INFILE}" OUTFILE="${OUTFILE}" 

magick -quiet "${INFILE}" \
  -filter LanczosRadius \
  -distort resize 1600 \
  -quality 92 \
  "${OUTFILE}"

The name of this script is Magick-Resize.sh

I would like to batch process a number of images using this script - that is, run it on multiple INFILES. Eg. If I have 100 images in a folder, I would like each of them to be processed once by this script, producing a unique OUTFILE for each.

I am very much a novice in bash. I gave it a crack with the below:

INSCRIPT=/path/Magick-Resize.sh

echo INSCRIPT="${INSCRIPT}"

for INFILE in *.tif; do
    if [[ "$INFILE" = *-tagged.tif ]]; then
        continue # skip output
    fi
    name=$(basename "$INFILE")-tagged.jpg
    echo name="${name}"
    "${INSCRIPT}" "$INFILE" > "${name}"
done

But in a test folder containing two .tif images, all it output was one image with the filename "*.jpg"

Is anyone able to provide a solution?

I'm on Mint 20.3

Answer 1

Your script doesn't take any argument, the names of the INFILE and OUTFILE are hardcoded within.

Here, I'd use zsh instead of bash, and do:

transform()
  magick -quiet $1 \
   -filter LanczosRadius \
   -distort resize 1600 \
   -quality 92 \
   $2

autoload -Uz zmv
zmv -P transform './(^*-tagged).tif' './$1-tagged.jpg'

Answer 2

I show another way to solve the problem: to modify the original code using bash.

• make one single shellscript
• put a shebang at the top, #!/bin/bash, to control which shell should run the script
• make a function instead of a separate shellscript of the 'doer' part.
• switch from magick to convert because that is how the Image Magick tool is implemented in my system. You can easily switch back to run it in your system.
• tweak the batch processing part to make it more robust.
  • add some # comments to help understanding what happens. When tagged files are encountered, skip, otherwise create a tagged jpg file
  • the bash variables for the file names are manipulated and tested in order to create only the desired files. This is described in man bash at the chapter about Parameter Expansion.

Please notice how the function doer is called with two parameters, and how they are seen as $1 and $2 in the function.

#! /bin/bash -

function doer() {
  INFILE="$1"
  OUTFILE="$2"
  #echo INFILE="${INFILE}" OUTFILE="${OUTFILE}" 
  convert -quiet "${INFILE}" \
    -filter LanczosRadius \
    -distort resize 1600 \
    -quality 92 \
    "${OUTFILE}"
}

#######
# main
#######

shopt -s nullglob
files=(./*.tif)
if (( ${#files[@]} )); then
  # there is at least one tif file, so continue
  for INFILE in "${files[@]}"; do
    if [[ "$INFILE" != *-tagged.tif ]]; then
      # not a tagged tif file, so create variable 'name'
      name="${INFILE%.tif}-tagged.jpg"
      if ! test -s "$name"; then
        # not a tagged jpg file, so create file 'name'
        printf '%s\n' "${name}"
        doer "$INFILE" "${name}"
      fi
    fi
  done
else
  echo >&2 "no tif files found"
  exit 1
fi
echo "normal termination"

Answer 3

I think this should be enough for your needs:

First enable extglob by running: shopt -s extglob and then

for i in !(*-tagged).tif; do 
    magick "./$i" <flags> "./${i%%.tif}-tagged.jpg"; 
done

This can also be trivially parallelized with GNU parallel:

parallel magick ./{} <flags> ./{.}-tagged.jpg ::: !(*-tagged).tif