Scripting with ImageMagick. Mass resize and add watermark to photos.

Tags : Linux, Software

ImageMagick mass resize

I take a lot of photos and standard result is 20MP image file sizing 4-10MB. It’s not big, but there are a lot of reasons you don’t want to throw original size photos on the web.

As a GNU/Linux long time user I resolve my problems by creating scripts and using already available tools.

I’ve created simple bash script to iterate by images, check if it wasn’t already resized and resize them to .

mkdir small
for file in $(find . -iname '*.jpg'); do
  if [ -f small/${file} ];
  then
    echo "File small/${file} exists."
  else
    echo -n Converting ${file}...
    convert -resize 2048\> "$file" "small/$file"
    echo done
  fi

done

You can find more information about CLI processing, resize and geometry.

TODO: I need to fix resize size for vertical images.

Add watermark

Until today I rarely added any watermarks or information about author into images.

After some big changes in my second blog I can put my photos as a file. I don’t need to use external services like 500px or SmugMug. I thought about property issues and content stealing.

There is problem and solution could by only similar - writing another script.

If you want to add watermark using ImageMagick you can do it using

composite -dissolve 50% -gravity south WATERMARK.png INPUT.jpg OUTPUT.jpg

Source: ImageMagick forum post

Mix resize and add watermark

You can pipe ImageMagick commands with miff:- as in example below

convert -resize 2048\> "INPUT_ORIGINAL_SIZE.jpg" miff:- | composite -quality 80 -dissolve 50% -gravity south WATERMARK.png  miff:- OUTPUT_RESIZED.jpg

I assumed JPEG quality as 80.

Mass resize and add watermark

Mixing all above knowledge I’ve upgraded my resize script to add watermark.

mkdir small
for file in $(find . -iname '*.jpg'); do
  if [ -f small/${file} ];
  then
   echo "File small/${file} exists."
  else
    echo -n Converting ${file}...
    convert -resize 2048\> "$file" miff:- | composite -quality 80 -dissolve 50% -gravity south ~/Obrazy/watermark.png  miff:- "small/$file"
    echo done
  fi

done

It’s a bit slower now, keep that in mind.

Protip: You can keep watermak file in somewhere else and use absolute path.