Bash batch resizing script using lanczos with imagemagicks convert

batch_resize.sh

#!/bin/bash

#### setup

print_error() {
        echo "$*"
        echo ""
        echo "Usage: $0 <Format> <Target Directory> <Files>"
        echo ""
        echo "Format: check out http://www.imagemagick.org/Usage/resize/#resize, f.e. 512x512"
        echo "Target Directory: directory where resized images will be placed"
        echo "Files: files to resize"
        echo ""
        echo "Example: $0 160x160 ./resized_160x160 *.jpg"
        exit 1;
}

CONVERT=`which convert`

[[ ! -x "${CONVERT}" ]] && print_error "convert not found, make sure you have imagemagick or compatible installed"

SIZE_SPEC=$1
TARGET_DIR=$2
shift
shift

[[ -z "$*" ]] &&  print_error "no files given"

#####

[[ ! -d "${TARGET_DIR}" ]] && mkdir -p ${TARGET_DIR}
for f in $*; do
        echo "Processing file ${f}..";
        ${CONVERT} ${f} -filter Lanczos -resize ${SIZE_SPEC} -background 'rgba(0,0,0,0)' ${TARGET_DIR}/${f}
done