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imagemagick

Comprehensive guide to image processing with ImageMagick’s magick CLI, including format conversion, resizing, transparency, optimization, compositing, metadata stripping, batch automation, and advanced manipulation techniques

Make background transparent

magick favicon.png \
  -fuzz 5% \
  -transparent "#1E2029" \
  -alpha on \
  -channel A -blur 0x1 -level 50%,100% +channel \
  favicon-transparent.png

Create favicon.ico the proper way

magick favicon.png \
 -background none \
 -define icon:auto-resize=16,32,48 \
 favicon.ico

Show version + supported formats (quick sanity check)

magick -version
magick -list format | less

Identify image info (dimensions, colorspace, alpha, etc.)

magick identify -verbose image.png | less

Convert between formats

magick input.webp output.png
magick input.png  output.jpg

Make background transparent

magick favicon.png \
  -fuzz 5% \
  -transparent "#1E2029" \
  -alpha on \
  -channel A -blur 0x1 -level 50%,100% +channel \
  favicon-transparent.png

Create favicon.ico the proper way

magick favicon.png \
 -background none \
 -define icon:auto-resize=16,32,48 \
 favicon.ico

Basics

Resize (keep aspect ratio)

magick input.png -resize 800x output.png

Resize to fit inside box (no upscaling)

magick input.jpg -resize 1920x1080\> output.jpg

Exact size crop from center (square thumbnail)

magick input.jpg -resize 512x512^ -gravity center -extent 512x512 thumb.png

Rotate + auto-orient from EXIF

magick input.jpg -auto-orient -rotate 90 output.jpg

Strip metadata (EXIF/IPTC) for smaller files

magick input.jpg -strip output.jpg

Optimize PNG (strip + max compression)

magick input.png -strip -define png:compression-level=9 output.png

Quality control for JPEG

magick input.jpg -strip -quality 85 output.jpg

Convert to grayscale

magick input.png -colorspace Gray output.png

Add a solid border

magick input.png -bordercolor "#1E2029" -border 20 output.png

Advanced techniques

Smart trim whitespace + add padding

magick input.png -trim +repage -bordercolor none -border 24 output.png

Remove a background color to alpha (more robust than -transparent)

magick input.png \
  -alpha set \
  -fuzz 7% \
  -fill none -draw "alpha 0,0 floodfill" \
  output.png

Feather edges of an alpha mask (clean cutouts)

magick input.png \
  -alpha on \
  -channel A -blur 0x2 -level 40%,100% +channel \
  output.png

Overlay a watermark (bottom-right, with opacity)

magick base.jpg \
  \( watermark.png -alpha on -channel A -evaluate multiply 0.35 +channel \) \
  -gravity southeast -geometry +30+30 -composite \
  out.jpg

Annotate text (with stroke for readability)

magick input.jpg \
  -gravity south -pointsize 42 \
  -fill white -stroke black -strokewidth 2 \
  -annotate +0+30 "wuseman" \
  out.jpg

Create a drop shadow for a transparent PNG

magick input.png \
  \( +clone -background black -shadow 60x6+0+12 \) \
  +swap -background none -layers merge +repage \
  out.png

Convert to WebP with good defaults (quality + metadata strip)

magick input.png -strip -quality 82 output.webp

Limit colors (e.g., for icons/pixel art)

magick input.png -dither FloydSteinberg -colors 32 output.png

Create a contact sheet from many images

magick *.jpg \
  -thumbnail 320x320^ -gravity center -extent 320x320 \
  -montage -tile 6x -geometry +12+12 \
  contact-sheet.png

Stack images vertically (append)

magick top.png bottom.png -append out.png

Stack images horizontally (+append)

magick left.png right.png +append out.png

Make a side-by-side diff (useful for before/after)

magick compare -metric AE before.png after.png diff.png 2>&1

Create a mask-based cutout (apply external alpha mask)

magick subject.png mask.png \
  -alpha off -compose CopyOpacity -composite \
  cutout.png

Batch / automation

Batch convert PNG → WebP (keeps filenames)

for f in *.png; do
  magick "$f" -strip -quality 82 "${f%.png}.webp"
done

Batch resize a folder into ./out (no upscaling)

mkdir -p out
for f in *.jpg; do
  magick "$f" -auto-orient -strip -resize 1920x1080\> "out/$f"
done

Safely handle spaces/newlines in filenames (find -print0)

mkdir -p out
find . -maxdepth 1 -type f -name '*.png' -print0 |
  while IFS= read -r -d '' f; do
    magick "$f" -strip -resize 1024x1024\> "out/${f#./}"
  done

Quick tips

Prefer explicit colorspace before heavy ops (avoid surprises)

magick input.png -colorspace sRGB -strip output.png

Use parentheses to isolate operations (critical for overlays)

magick base.png \
  \( overlay.png -resize 25% \) \
  -gravity center -composite out.png