ImageMagick notes on image processing

Repository is here, official website and docs are here.

Remove metadata for privacy

magick input.jpg -strip output.jpg

Removing only location data, requires exiftool:

exiftool -gps:all= -o output.jpg input.jpg
# or
exiftool -gps:all= -overwrite_original input.jpg

Remove excess whitespace

Trim unused blank space, useful especially for logos:

magick input.png -strip -trim +repage output.png

Center crop

Can be used for fixed size blog post items.

magick input.jpg \
  -strip \
  -resize 800x600^ \
  -gravity center \
  -extent 800x600 \
  -quality 82 \
  -define webp:method=6 \
  output.webp

Convert to WebP

Assets published on the web are better of if uploaded in WebP, providing lower sizes for the same quality compared to JPEG.

The webp:method flag below defines compression effort, taking values between 0 and 6. For non-realtime conversions, keeping it 6 provides the best compression effort.

magick input.jpg \
  -strip \
  -quality 86 \
  -define webp:method=6 \
  output.webp

Resize + convert:

magick input.jpg \
  -strip \
  -resize 1200x \
  -quality 86 \
  -define webp:method=6 \
  -unsharp 0x0.75+0.75+0.008 \
  output.webp

-unsharp 0x0.75+0.75+0.008 values are good with resizing along with web publishing.

Lossless:

magick input.png \
  -strip \
  -define webp:lossless=true \
  output.webp

Batch:

for f in *.jpg; do
  magick "$f" -strip -quality 86 -define webp:method=6 "${f%.jpg}.webp"
done