Resize an image from a local file or URL

resize-img

#!/usr/bin/env bash

# Resizes an image from either a local file or a URL passed on the command line or to stdin,
# and prints the resized image file path to stdout.
#
# Options:
#
# resize-img -h
#
# Examples:
#
# resize-img -i ./input.png -o ./output.png -p "50%"
#
# resize-img -i "https://example.com/input.gif" -o ./output.gif -w 1024
#
# echo input.png | resize-img -o ./output.png -w 1200
#

# Exit on first error
set -e

# Debug
#set -x

# Checks that a command is installed
installed () { command -v "${1}" >/dev/null 2>&1 || { >&2 echo "Cannot execute the ${1} command"; exit 1; } }

# Checks that a file is valid
validfile() { [[ -r ${1} ]]; }

# Checks if a variable is empty
empty () { [[ -z $1 ]]; }

# Checks that a URL is valid (attempts to fetch it)
validurl ()
{
  # Read the first byte from the URL
  if curl --output /dev/null  --silent --fail -r 0-0 "${1}"; then
     return 0
  else
     return 1
  fi
}

help () {
  scriptName=$(basename $0)
  echo $scriptName [options]
  echo
  echo Options:
  echo
  echo "--help, -h     Prints this help"
  echo "--input, -i    The file or URL for the image to resize"
  echo "--output, -o   The image file to create"
  echo "--percent, -p  The percentage to resize the image"
  echo "--width, -w    The width of the output image"
  echo
  echo Example:
  echo
  echo
  echo $scriptName --intput "./input.gif" --output "./output.gif" --width 1024
  echo
}

installed convert # From Imagemagick
installed curl

percent=50
width=
input=
outputFile=

if [[ $# = 0 ]]; then
   help
   exit 1
fi

while [[ $# != 0 ]]; do
   case "${1}" in
      -h|--help)
         help
         exit 0
         ;;
      -i|--input)
         input="$2"
         shift 2
         ;;
      -o|--output)
         outputFile="${2}"
         shift 2
         ;;
      -p|--percent)
         percent="${2}"
         shift 2
         ;;
      -w|--width)
         width="${2}"
         shift 2
         ;;
      *)
         shift
         ;;
   esac
done

# Accept input name on stdin too
if [[ -z $input ]]; then
   input=$(cat)
fi

# Check the parameters
if [[ -z $input ]]; then
   >&2 echo "No file or URL was provided"
   exit 1
fi

imgFile=

if validfile "${input}"; then
  imgFile="${input}"
elif validurl "${input}"; then
  # Download it to a tmp file.
  tmpfile=$(mktemp /tmp/resize-img-XXXXXX)
  curl --location --output "${tmpfile}" --silent "${input}"

  # Add a file extension to the tmp file so the output file has the extension too.
  ext=$(grep "$(file -b --mime-type "${tmpfile}")" /etc/mime.types | awk '{print $2}')
  if [[ ! -z ${ext} ]]; then
    mv "${tmpfile}" "${tmpfile}.${ext}"
    tmpfile="${tmpfile}.${ext}"
  fi

  # Remove the tmp file when we're done.
  trap 'rm -f ${tmpfile}' EXIT INT

  imgFile="${tmpfile}"
else
  >&2 echo "${input} cannot be read"
  exit 1
fi

if empty "$outputFile"; then
   if empty "$width"; then
      outputFile=$(echo "${imgFile}" | sed -E "s|(.*)(\..*)|\1_${percent}_percent\2|")
   else
      outputFile=$(echo "${imgFile}" | sed -E "s|(.*)(\..*)|\1_${width}\2|")
   fi
fi

if [[ ! -z ${width} ]]; then
   convert -resize "${width}" "${imgFile}" "${outputFile}"
elif [[ ! -z ${percent} ]]; then
   convert -resize "${percent}"% "${imgFile}" "${outputFile}"
else
   >&2 echo "No percent or width provided"
fi

if [[ -r ${outputFile} ]]; then
   echo "${outputFile}"
   exit 0
else
   >&2 echo "${outputFile} was not created"
   exit 1
fi