Convert an image to monochrome

monochrome.sh

#!/bin/bash

# Turn any image to monochrome
# -- Cole Hocking

# -----------------------------------------------------------------------------
# Verify Homebrew installation for package management
# Docs: https://brew.sh/
go_brew() {    
    echo "Checking for Homebrew package management tool..."
    if [[ -f "$(which brew)" ]]; then
        echo "Brew is installed!"
        exit $?
    else
        echo "Homebrew is not installed. Please follow the prompts for installation."
        echo "(requires sudo for installation)" 
        /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
    fi
    # Confirm that brew is installed before we continue
    sync
    if  [[ ! -f "$(which brew)" ]]; then 
        echo 'Brew does not installed or installation aborted. Re-run ./monochrome.sh ' > 2
        exit 1
    else
        echo "Brew has been installed successfully!"
    fi
}
# -----------------------------------------------------------------------------
# verify imagemagick installation
go_magick() {    
    echo "Checking for ImageMagick..."
    if [[ -f "$(which magick)" ]]; then
        echo "ImageMagick is installed!"
    else
        echo "ImageMagick is not installed. Installing..."
        brew install imagemagick
    fi
    # Confirm that brew is installed before we continue
    sync
    if  [[ ! -f "$(which magick)" ]]; then 
        echo 'ImageMagick does not installed or installation aborted. Re-run ./monochrome.sh ' > 2
        exit 1
    else
        echo "ImageMagick has been installed successfully!"
    fi
}
# -----------------------------------------------------------------------------
# main call
main() {
  # check that infile/outfile supplied
  if [[ $# -ne 2 ]]; then
    echo "Usage: ./monochrome.sh <input_file.jpg> <output_file.png>"
    exit(1)
  else
    # set input file
    INFILE="$1"
    # set output file
    OUTFILE="$2"
  fi
  # check for homebrew
  go_brew 
  # check for imagemagick
  go_magick
  # convert the images
  magick "${INFILE}" -monochrome "${OUTFILE}"
  echo "Image converted to: ${OUTFILE}"
  echo "Done!"
}
# call main
main