watermark imagemagick - add transparent png to all images in a folder as percentage width of the original

README.md

Image magick Watermark example

Create a watermark image, should be transparent background. watermark.png

Run script in the folder where all jpgs are located:

cd someproductimages
bash ../watermark.sh
...

watermark.sh

# make sure there are no spaces in filenames 
rename  's/ +/_/g' *.jpg

# path to watermark image
watermark="../watermark.png"

# create extra folder in current folder
mkdir -p watermark

for i in `ls *jpg`
do
  # calculate width of watermark: e.g. 1/3 of width
  echo "processing $i"
  full_width=`identify -format '%w' ""$i""`
  width=`expr $full_width / 3`
  echo "Watermark size: $width / $full_width"
  composite -geometry x$width+15+15 -dissolve 50% -gravity SouthWest $watermark "$i" "watermark/$i"
done