imagemagick Skill

Advanced image processing - format conversion, resizing, effects, transformations, batch operations.

When to Use

Use imagemagick when you need:

  • Convert image formats
  • Resize/crop images
  • Apply effects/filters
  • Create thumbnails
  • Batch process images
  • Add watermarks/text
  • Optimize for web

Quick Start

Invoke the Skill

"Use imagemagick to:
- Resize all product images to 800x800
- Convert to WebP
- Optimize file size
- Keep quality high"

What You Get

The skill will help you:

  1. Convert formats
  2. Resize/transform
  3. Apply effects
  4. Batch process
  5. Optimize output

Common Use Cases

Format Conversion

"Use imagemagick to convert all PNG images to JPEG with 90% quality"

Create Thumbnails

"Use imagemagick to create 200x200 thumbnails for all images in folder"

Watermark Images

"Use imagemagick to add logo watermark to bottom-right of all images"

Batch Optimization

"Use imagemagick to optimize all images for web:
- Max width 1920px
- WebP format
- Good quality
- Small file size"

Basic Operations

Format Conversion

# PNG to JPEG
magick input.png output.jpg

# With quality setting
magick input.png -quality 85 output.jpg

# To WebP
magick input.jpg output.webp

Resize

# Fit within 800x600 (maintains aspect)
magick input.jpg -resize 800x600 output.jpg

# Exact size (may distort)
magick input.jpg -resize 800x600! output.jpg

# Width only
magick input.jpg -resize 800x output.jpg

# Height only
magick input.jpg -resize x600 output.jpg

# By percentage
magick input.jpg -resize 50% output.jpg

Crop

# Crop to 500x500 from top-left
magick input.jpg -crop 500x500+0+0 output.jpg

# Crop from center
magick input.jpg -gravity center -crop 500x500+0+0 output.jpg

Rotate

# Rotate 90 degrees
magick input.jpg -rotate 90 output.jpg

# Flip horizontal
magick input.jpg -flop output.jpg

# Flip vertical
magick input.jpg -flip output.jpg

Effects & Filters

Blur/Sharpen

# Blur
magick input.jpg -blur 0x8 output.jpg

# Sharpen
magick input.jpg -sharpen 0x1 output.jpg

Adjust Colors

# Brightness (+/- 50)
magick input.jpg -modulate 120 output.jpg

# Contrast
magick input.jpg -contrast output.jpg

# Saturation
magick input.jpg -modulate 100,150 output.jpg

# Grayscale
magick input.jpg -colorspace Gray output.jpg

# Sepia tone
magick input.jpg -sepia-tone 80% output.jpg

Borders & Frames

# Add border
magick input.jpg -border 10 -bordercolor black output.jpg

# Add frame
magick input.jpg -mattecolor white -frame 10x10 output.jpg

Watermark

# Add logo
magick input.jpg logo.png -gravity southeast -geometry +10+10 -composite output.jpg

# Add text
magick input.jpg -gravity southeast -pointsize 20 -fill white -annotate +10+10 'Copyright 2025' output.jpg

Batch Processing

Convert All Files

# Convert all PNG to JPEG
for file in *.png; do
  magick "$file" "${file%.png}.jpg"
done

Batch mogrify

# Resize all JPEGs in place
mogrify -resize 800x600 *.jpg

# Convert all to WebP
mogrify -format webp *.jpg

Advanced Batch

# Create thumbnails for all images
for file in *.jpg; do
  magick "$file" -resize 200x200^ -gravity center -extent 200x200 "thumb_${file}"
done

Web Optimization

Progressive JPEG

magick input.jpg -interlace Plane -quality 85 output.jpg

Strip Metadata

magick input.jpg -strip output.jpg

Optimize WebP

magick input.jpg -quality 80 -define webp:method=6 output.webp

Create Responsive Sizes

# Create multiple sizes
magick input.jpg -resize 1920x output-large.jpg
magick input.jpg -resize 1280x output-medium.jpg
magick input.jpg -resize 640x output-small.jpg

Advanced Features

Create Montage

# Create contact sheet
montage *.jpg -thumbnail 200x200 -geometry +5+5 montage.jpg

Composite Images

# Overlay two images
composite overlay.png background.jpg output.jpg

Create Animated GIF

magick -delay 100 -loop 0 frame*.jpg animated.gif

Extract Frames from GIF

magick animated.gif frame_%03d.jpg

Geometry Specs

  • 100x100 - Fit within (maintains aspect)
  • 100x100! - Exact size (may distort)
  • 100x100^ - Fill (may crop)
  • 100x - Width 100, auto height
  • x100 - Height 100, auto width
  • 50% - Scale to 50%
  • 100x100+10+20 - 100x100 at offset (10,20)

Quick Examples

Simple Resize:

"Use imagemagick to resize image to 800px width"

Batch Thumbnails:

"Use imagemagick to create square 300x300 thumbnails for all product images"

Format Conversion:

"Use imagemagick to convert all images to WebP format with good compression"

Add Watermark:

"Use imagemagick to add copyright text to bottom-right of all images"

Best Practices

  1. Always backup originals
  2. Test on single file first
  3. Use appropriate quality (85-90 for web)
  4. Strip metadata for web
  5. Maintain aspect ratio
  6. Use WebP for modern browsers
  7. Create multiple sizes for responsive
  8. Optimize file size

Common Tasks

Product Images

# Square crop from center
magick input.jpg -resize 1000x1000^ -gravity center -extent 1000x1000 product.jpg

Social Media

# Instagram (1080x1080)
magick input.jpg -resize 1080x1080^ -gravity center -extent 1080x1080 instagram.jpg

# Facebook cover (820x312)
magick input.jpg -resize 820x312^ -gravity center -extent 820x312 facebook.jpg

Email Friendly

# Small file size
magick input.jpg -resize 600x -quality 70 -strip email.jpg

Troubleshooting

Command not found

# Check installation
magick -version

# Install
brew install imagemagick  # macOS
sudo apt-get install imagemagick  # Linux

Security policy

Edit /etc/ImageMagick-7/policy.xml or use convert instead of magick.

Quality issues

  • Increase quality value (-quality 90)
  • Use PNG for graphics/screenshots
  • Use JPEG for photos
  • Use WebP for best compression

Next Steps

Bottom Line: imagemagick handles all image processing. Resize, convert, optimize - powerful command-line image manipulation.