How To: Auto Convert iPhone Images to BW and shrink for receipts

I’ve been taking pictures of receipts with my iPhone and needed a very simple system to convert the 1MB+ JPEG images to Greyscale and downsize to something smaller than 2448 x 3264.

The answer was a combination of ImageMagick and MacOS X Automator.


  • Make sure Xcode is installed through AppStore. (Free)
  • open a terminal, run
    xcode-select --install
  • Agree to Xcode license in Terminal: sudo xcodebuild -license
    sudo xcodebuild -license
  • and select MacPorts for your version of MacOS X.
  • Download and run the installer.
  • Back to terminal and run the below (will take a while to download all dependancies.)
    sudo port install ImageMagick
  • Now we can start to play. Open Automator (comes with Mac OS X)
  • File -> New

Follow Image below:


Add the below code:

for f in "$@"
/opt/local/bin/convert "$f" -colorspace Gray -resize 640 "$f"

Now we can drag any images onto the and they will be converted from 1.7MB RGB to 70-100KB Greyscale and look great.


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