comp

#!/usr/bin/env bash

: '
    Compares two directories of images.

    If the directories contain differently named files, the comparison terminates.

    Otherwise, we use ImageMagick to compare the content of pairs of images by name.

    If a pair of images are not identical, we generate an animated gif "flicker" diagram to assist in visually
    highlighting the differences.
'

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 [[ $# -ne 4 ]]; then
  logError "${ME}" "Usage DIR1 DIR2 FORMAT OUT_DIR."; exit 1
fi

ERRORS=0
DIR1="${1}" && readonly DIR1
# Ensure that the input directories exit
if [ ! -d "${DIR1}" ]; then
  ERRORS=1 && logError "First image directory not accessible at $(sQuote "$(red "${DIR1}")")"
fi

DIR2="${2}" && readonly DIR2
if [ ! -d "${DIR2}" ]; then
  ERRORS=1 && logError "${ME}" "Second image directory not accessible at $(sQuote "$(red "${DIR2}")")"
fi

FORMAT="${3}" && readonly FORMAT

if [ "${DIR1}" == "${DIR2}" ]; then
  ERRORS=1 && logError "${ME}" "Both arguments point to the same directory $(sQuote "$(red "${DIR1}")")"
fi

# Ensure that Image Magick is installed
identify -version &>/dev/null \
  || { ERRORS=1 && logError "${ME}" "ImageMagick $(sQuote "$(blue "identify")") not found on the system."; }

# Create the output directory if there's no errors up to this point
OUT_DIR="${4}"
readonly OUT_DIR
if [ "$ERRORS" -eq "0" ]; then
  if [ ! -d "${OUT_DIR}" ]; then
    logInfo "${ME}" "Creating output directory $(sQuote "$(green "${OUT_DIR}")")"
    if ! mkdir -p  "${OUT_DIR}"; then
      ERRORS=1 && logError "${ME}" "Could not create output directory."
    fi
  fi
fi

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

FILESET_1=$(find "${DIR1}" -iname "*.${FORMAT}" -exec basename {} \; | sort);
readonly FILESET_1

FILESET_2=$(find "${DIR2}" -iname "*.${FORMAT}" -exec basename {} \; | sort);
readonly FILESET_2

logInfo "${ME}" "Comparing filesets by name only."
if ! comm -3 <(echo "${FILESET_1[@]}") <(echo "${FILESET_2[@]}"); then
  logError "${ME}" "Directories contain differently named files, exiting." && exit 1
else
  logInfo "${ME}" "Both filesets contain identically named files."
fi

logInfo "${ME}" "Comparing images by ImageMagick signature."
for BASENAME in ${FILESET_1}; do
  FIRST_FILE="${DIR1}/${BASENAME}"
  SECOND_FILE="${DIR2}/${BASENAME}"
  FIRST_SIGNATURE=$(identify -quiet -format "%#" "${FIRST_FILE}")
  SECOND_SIGNATURE=$(identify -quiet -format "%#" "${SECOND_FILE}")
  if [ "${FIRST_SIGNATURE}" != "${SECOND_SIGNATURE}" ]; then
    FLICKER_FILE="${OUT_DIR}/flicker_${BASENAME%.*}.gif"
    logInfo "${ME}" "Differences in $(sQuote "$(blue "${BASENAME}")"), generating flicker animation as $(sQuote "$(blue "${FLICKER_FILE}")")"
    "${SCRIPT_PATH}"/flicker "${FIRST_FILE}" "${SECOND_FILE}" "${FLICKER_FILE}"
  fi
done