Hue rotation script for batch image conversion (Created for modifying fingerprint scanner animation on OnePlus6T)

hsl.sh

#!/usr/bin/env bash
# Batch hue rotation script using ImageMagick's 'convert'

INPUT_DIR=$(pwd)/input
OUTPUT_DIR=$(pwd)/output-$1

if [ -z "$1" ] || [ "$1" -lt 100 ] || [ "$1" -gt 300 ];
then
    echo "Specify a hue rotation value between 100 and 300. 100 is 'no rotation' and 300 is 'full rotation'"
    echo "Usage: $0 <value>"
    echo "Output will be placed in a directory named $OUTPUT_DIR<value>"
    exit 1
fi

if [ ! -d "$INPUT_DIR" ];
then
    echo "Input directory not found: $INPUT_DIR"
    exit 1
fi

if [ -z "$(ls -A "$INPUT_DIR")" ];
then
    echo "Input directory is empty: $INPUT_DIR"
    exit 1
fi

if [ -d "$OUTPUT_DIR" ] && [ ! -z "$(ls -A "$OUTPUT_DIR")" ];
then
    echo "WARNING: Output directory is not empty. Exiting so I don't overwrite your files. Move them and run again."
    exit 1
elif [ ! -d "$OUTPUT_DIR" ];
then
    mkdir "$OUTPUT_DIR"
fi

INPUT_FILES=()
while IFS=  read -r -d $'\0'; do
    INPUT_FILES+=("$REPLY")
done < <(find "$INPUT_DIR" -type f -name "*.png" -printf "%f\0")

for i in "${INPUT_FILES[@]}";
do
    convert -debug "Resource" "$INPUT_DIR/$i" -set option:modulate:colorspace hsb -modulate 100,100,"$1" "$OUTPUT_DIR/$i"
done

Example. Number at end of file name is rotation value.