flicker

#!/usr/bin/env bash

: '
    Generates a flicker animation for a pair of images using ImageMagick.
'

ME=$(basename "$0") && readonly ME
# shellcheck disable=SC2164
SCRIPT_PATH="$( cd -- "$(dirname "$0")" >/dev/null 2>&1 ; pwd -P )"
readonly SCRIPT_PATH

source "${SCRIPT_PATH}"/common

if [[ $# -ne 3 ]]; then
  logError "${ME}" "Usage: flicker $(blue "FILE1") $(blue "FILE2") $(green "OUTPUT_FILE")"; exit 1
fi

ERRORS=0
if [ ! -f "${1}" ]; then
  ERRORS=1 && logError "${ME}" "First file not accessible at $(sQuote "$(red "${1}")")"
fi

if [ ! -f "${2}" ]; then
  ERRORS=1 && logError "${ME}" "Second file not accessible at $(sQuote "$(red "${2}")")"
fi

if [ "${1}" == "${2}" ]; then
  ERRORS=1 && logError "${ME}" "Both input files are the same $(sQuote "$(red "${1}")")"
fi

if [ -f "${3}" ]; then
  ERRORS=1 && logError "${ME}" "Output file $(sQuote "$(red "${3}")") already exists."
fi

# Ensure that the ImageMagick 'animate' command is installed
animate -version &>/dev/null || \
  { ERRORS=1 && logError "${ME}" "ImageMagick $(sQuote "$(red "animate")") command not found." ; }
# Ensure that the ImageMagick 'convert' command is installed
convert -version &>/dev/null || \
  { ERRORS=1 && logError "${ME}" "ImageMagick $(sQuote "$(red "convert")") command not found." ; }

# If there's any error, exit
if [ "$ERRORS" -ne "0" ]; then
  logError "${ME}" "Exiting due to previous errors."; exit 1
else
  convert -delay 25 -loop 0 "${1}" "${2}" "${3}"
fi