Image Manipulator

Image Manipulator Skill

Expert in image manipulation and transformation using ImageMagick command-line tools.

Core Capabilities

• Rotation & Orientation: Rotate, flip, auto-orient images
• Resizing & Scaling: Resize, scale, thumbnail generation with aspect ratio preservation
• Cropping: Crop to specific dimensions or percentages
• Format Conversion: Convert between formats (JPG, PNG, WEBP, GIF, PDF, etc.)
• Quality & Compression: Adjust quality, optimize file size
• Filters & Effects: Blur, sharpen, grayscale, sepia, edge detection
• Watermarks & Overlays: Add text or image watermarks
• Batch Processing: Process multiple images with same operations
• Metadata: View and edit EXIF data
• Advanced: Color adjustments, transformations, distortions

When to Use This Skill

Use this skill when users request:

• "Rotate this image 90 degrees"
• "Resize image to 800x600"
• "Convert PNG to JPG"
• "Add watermark to image"
• "Crop this image"
• "Make image grayscale"
• "Batch resize all images in folder"
• "Compress image to reduce file size"

Prerequisites

Installation

macOS:

brew install imagemagick

Ubuntu/Debian:

sudo apt-get update
sudo apt-get install imagemagick

Verification:

magick -version

ImageMagick Version Differences

ImageMagick 7+ (RECOMMENDED):

• Use magick command for all operations
• Example: magick input.jpg -resize 50% output.jpg

ImageMagick 6 (Legacy):

• Uses convert command
• Example: magick input.jpg -resize 50% output.jpg

Note: This skill uses ImageMagick 7 syntax (magick) throughout. If you have ImageMagick 6, replace magick with convert in all commands.

Basic Operations

1. Rotation

Rotate by specific angle:

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

# Rotate 10 degrees clockwise
magick input.jpg -rotate 10 output.jpg

# Rotate counter-clockwise (negative angle)
magick input.jpg -rotate -45 output.jpg

# Rotate with white background fill
magick input.jpg -background white -rotate 15 output.jpg

# Rotate with transparent background (PNG)
magick input.png -background none -rotate 30 output.png

Flip/Mirror:

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

# Flip horizontally (mirror)
magick input.jpg -flop output.jpg

# Auto-orient based on EXIF data
magick input.jpg -auto-orient output.jpg

2. Resizing & Scaling

Resize to exact dimensions:

# Resize to 800x600 (may distort)
magick input.jpg -resize 800x600! output.jpg

# Resize maintaining aspect ratio (fit within 800x600)
magick input.jpg -resize 800x600 output.jpg

# Resize width only (height auto)
magick input.jpg -resize 800x output.jpg

# Resize height only (width auto)
magick input.jpg -resize x600 output.jpg

# Resize by percentage
magick input.jpg -resize 50% output.jpg

Thumbnail generation:

# Create thumbnail (max 200x200, preserve aspect ratio)
magick input.jpg -thumbnail 200x200 thumbnail.jpg

# Create square thumbnail (crop to center)
magick input.jpg -thumbnail 200x200^ -gravity center -extent 200x200 thumbnail.jpg

Scale (faster, lower quality):

# Quick scale for previews
magick input.jpg -scale 50% preview.jpg

3. Cropping

Crop to dimensions:

# Crop 800x600 from top-left corner
magick input.jpg -crop 800x600+0+0 output.jpg

# Crop 800x600 starting at position (100,50)
magick input.jpg -crop 800x600+100+50 output.jpg

# Crop from center
magick input.jpg -gravity center -crop 800x600+0+0 output.jpg

# Crop by percentage (50% of original)
magick input.jpg -crop 50%x50%+0+0 output.jpg

Auto-crop (remove borders):

# Remove white borders
magick input.jpg -fuzz 10% -trim output.jpg

# Remove borders and add 10px padding
magick input.jpg -fuzz 10% -trim +repage -bordercolor white -border 10 output.jpg

4. Format Conversion

Convert between formats:

# PNG to JPG
magick input.png output.jpg

# JPG to PNG
magick input.jpg output.png

# Any format to WEBP
magick input.jpg -quality 80 output.webp

# PDF to JPG (first page)
magick input.pdf[0] output.jpg

# Multiple images to PDF
magick image1.jpg image2.jpg image3.jpg output.pdf

# GIF to individual frames
magick animation.gif frame-%03d.png

Quality settings:

# High quality JPG
magick input.jpg -quality 95 output.jpg

# Compressed JPG
magick input.jpg -quality 60 output.jpg

# PNG compression
magick input.png -quality 85 output.png

# WEBP with quality
magick input.jpg -quality 80 output.webp

5. Filters & Effects

Grayscale & Sepia:

# Convert to grayscale
magick input.jpg -colorspace Gray output.jpg

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

Blur & Sharpen:

# Blur (radius x sigma)
magick input.jpg -blur 0x8 output.jpg

# Gaussian blur
magick input.jpg -gaussian-blur 5x2 output.jpg

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

# Unsharp mask (radius x sigma + amount + threshold)
magick input.jpg -unsharp 0x5+0.5+0 output.jpg

Edge & Enhance:

# Edge detection
magick input.jpg -edge 1 output.jpg

# Enhance (reduce noise)
magick input.jpg -enhance output.jpg

# Contrast stretch
magick input.jpg -contrast-stretch 0 output.jpg

Brightness & Contrast:

# Increase brightness (+20)
magick input.jpg -modulate 120 output.jpg

# Decrease brightness (-20)
magick input.jpg -modulate 80 output.jpg

# Adjust contrast
magick input.jpg -contrast output.jpg
magick input.jpg +contrast output.jpg  # Reduce

# Auto-level (normalize)
magick input.jpg -auto-level output.jpg

Color adjustments:

# Negate (invert colors)
magick input.jpg -negate output.jpg

# Posterize (reduce colors)
magick input.jpg -posterize 8 output.jpg

# Adjust saturation (+50%)
magick input.jpg -modulate 100,150 output.jpg

# Desaturate (-50%)
magick input.jpg -modulate 100,50 output.jpg

6. Watermarks & Overlays

Text watermark:

# Simple text watermark
magick input.jpg -gravity southeast -pointsize 30 -fill white \
  -annotate +10+10 "Copyright 2025" output.jpg

# Text with shadow
magick input.jpg -gravity southeast -pointsize 40 -fill white \
  -stroke black -strokewidth 2 -annotate +20+20 "Watermark" output.jpg

# Semi-transparent text
magick input.jpg -gravity center -pointsize 60 -fill "rgba(255,255,255,0.5)" \
  -annotate +0+0 "DRAFT" output.jpg

Image watermark:

# Overlay logo (bottom-right)
magick input.jpg logo.png -gravity southeast -geometry +10+10 \
  -composite output.jpg

# Semi-transparent overlay
magick input.jpg \( logo.png -alpha set -channel A -evaluate multiply 0.5 +channel \) \
  -gravity center -composite output.jpg

7. Borders & Frames

Add borders:

# Simple border
magick input.jpg -border 10x10 -bordercolor black output.jpg

# Colored border
magick input.jpg -border 20x20 -bordercolor "#FF5733" output.jpg

# Frame with shadow
magick input.jpg -mattecolor gray -frame 10x10+5+5 output.jpg

8. Batch Processing

Process multiple images:

# Resize all JPGs in directory
for img in *.jpg; do
  magick "$img" -resize 800x600 "resized_$img"
done

# Convert all PNGs to JPG
for img in *.png; do
  magick "$img" "${img%.png}.jpg"
done

# Add watermark to all images
for img in *.jpg; do
  magick "$img" -gravity southeast -pointsize 30 -fill white \
    -annotate +10+10 "© 2025" "watermarked_$img"
done

Mogrify (in-place editing):

# Resize all JPGs in place (overwrites originals!)
mogrify -resize 800x600 *.jpg

# Convert format in place
mogrify -format png *.jpg

# Rotate all images
mogrify -rotate 90 *.jpg

9. Image Information

Get image details:

# Basic info
identify input.jpg

# Detailed info
identify -verbose input.jpg

# Specific properties
identify -format "%wx%h" input.jpg  # Width x Height
identify -format "%b" input.jpg     # File size
identify -format "%m" input.jpg     # Format

# EXIF data
identify -format "%[EXIF:*]" input.jpg

10. Advanced Operations

Combine images:

# Append horizontally
magick image1.jpg image2.jpg +append output.jpg

# Append vertically
magick image1.jpg image2.jpg -append output.jpg

# Create montage/grid
montage *.jpg -tile 3x3 -geometry +5+5 montage.jpg

Transparency:

# Make white background transparent
magick input.jpg -transparent white output.png

# Make specific color transparent
magick input.jpg -fuzz 10% -transparent "#FFFFFF" output.png

# Add alpha channel
magick input.jpg -alpha set output.png

Perspective & Distortion:

# Perspective distortion
magick input.jpg -distort Perspective "0,0 20,60  90,0 70,63  0,90 5,83  90,90 85,88" output.jpg

# Barrel distortion
magick input.jpg -distort Barrel "0.0 0.0 -0.3" output.jpg

Common Workflows

Workflow 1: Prepare Image for Web

# Resize, compress, and optimize for web
magick input.jpg \
  -resize 1200x1200 \
  -quality 85 \
  -strip \
  output.jpg

Explanation:

• Resize to max 1200x1200 (maintains aspect ratio)
• Set quality to 85% (good balance)
• Strip metadata to reduce file size

Workflow 2: Create Thumbnail Gallery

# Create thumbnails
for img in *.jpg; do
  magick "$img" -thumbnail 200x200^ -gravity center -extent 200x200 "thumb_$img"
done

# Create montage
montage thumb_*.jpg -tile 5x -geometry +2+2 gallery.jpg

Workflow 3: Batch Straighten Scanned Documents

# Deskew (auto-straighten) all scans
for img in scan_*.jpg; do
  magick "$img" -deskew 40% "straight_$img"
done

Workflow 4: Add Copyright to All Photos

# Add semi-transparent copyright text
for img in photo_*.jpg; do
  magick "$img" \
    -gravity southeast \
    -pointsize 24 \
    -fill "rgba(255,255,255,0.7)" \
    -annotate +10+10 "© 2025 Your Name" \
    "copyright_$img"
done

Workflow 5: Convert and Optimize for Email

# Resize to email-friendly size and compress
magick large_image.jpg \
  -resize 800x800 \
  -quality 70 \
  -strip \
  email_image.jpg

Best Practices

1. Preserve Originals

Always work on copies or use different output names:

# Good
magick original.jpg -resize 50% resized.jpg

# Risky (overwrites original with mogrify)
mogrify -resize 50% original.jpg

2. Quality Settings

• High quality: -quality 95 (large files)
• Good quality: -quality 85 (recommended for web)
• Acceptable: -quality 70-80 (smaller files)
• Low quality: -quality 60 (very small, visible artifacts)

3. Format Selection

• JPG: Photos, images with gradients (lossy compression)
• PNG: Images with transparency, sharp edges, text (lossless)
• WEBP: Modern web format (better compression than JPG/PNG)
• GIF: Simple animations, limited colors
• TIFF: Professional/archival (lossless, large files)

4. Aspect Ratio

• Use -resize WxH (without !) to maintain aspect ratio
• Use -resize WxH! to force exact dimensions (may distort)
• Use -thumbnail for better quality small images

5. Background Color

When rotating with transparent areas:

• JPG: Use -background white (no transparency support)
• PNG: Use -background none (preserve transparency)

6. Performance

• Use -strip to remove metadata and reduce file size
• Use -thumbnail instead of -resize for small images (faster)
• Use -scale for quick previews (lower quality, much faster)
• Consider batch processing at night for large operations

Common Use Cases

Passport/ID Photo Processing

# Straighten scanned passport
magick passport_scan.jpg -rotate 10 -background white straightened.jpg

# Crop to passport photo
magick photo.jpg -crop 600x600+100+50 passport_photo.jpg

# Resize to standard passport size (2x2 inches at 300 DPI = 600x600 pixels)
magick photo.jpg -resize 600x600! -quality 95 passport.jpg

Social Media Optimization

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

# Facebook cover (820x312)
magick banner.jpg -resize 820x312! facebook_cover.jpg

# Twitter header (1500x500)
magick header.jpg -resize 1500x500! twitter_header.jpg

Document Scanning

# Enhance scanned document
magick scan.jpg \
  -deskew 40% \
  -auto-level \
  -sharpen 0x1 \
  -quality 90 \
  enhanced_scan.jpg

# Convert to PDF
magick scan_page1.jpg scan_page2.jpg scan_page3.jpg document.pdf

Troubleshooting

"convert: not found"

Solution:

# Check if ImageMagick is installed
which convert

# Install if missing
brew install imagemagick  # macOS
sudo apt-get install imagemagick  # Ubuntu

ImageMagick 7+ Command Differences

ImageMagick 7 uses magick instead of convert:

# ImageMagick 6
magick input.jpg output.png

# ImageMagick 7 (both work)
magick input.jpg output.png
magick magick input.jpg output.png

Large File Processing

For very large images:

# Limit memory usage
magick -limit memory 256MiB -limit map 512MiB input.jpg output.jpg

# Use streaming for huge files
stream -map rgb -storage-type char input.jpg output.rgb

Permission Errors with PDFs

Edit /etc/ImageMagick-6/policy.xml (or similar) and comment out PDF restrictions:

<!-- <policy domain="coder" rights="none" pattern="PDF" /> -->

Quick Reference

Rotation

magick input.jpg -rotate 90 output.jpg           # Clockwise 90°
magick input.jpg -rotate -45 output.jpg          # Counter-clockwise 45°
magick input.jpg -flip output.jpg                # Vertical flip
magick input.jpg -flop output.jpg                # Horizontal flip

Resize

magick input.jpg -resize 800x600 output.jpg      # Fit in 800x600
magick input.jpg -resize 50% output.jpg          # Scale to 50%
magick input.jpg -thumbnail 200x200 output.jpg   # Thumbnail

Crop

magick input.jpg -crop 800x600+0+0 output.jpg    # Crop from top-left
magick input.jpg -gravity center -crop 500x500+0+0 output.jpg  # Center crop

Convert

magick input.png output.jpg                       # PNG to JPG
magick input.jpg -quality 85 output.jpg           # Compress JPG
magick *.jpg output.pdf                           # Images to PDF

Effects

magick input.jpg -colorspace Gray output.jpg      # Grayscale
magick input.jpg -blur 0x8 output.jpg             # Blur
magick input.jpg -sharpen 0x1 output.jpg          # Sharpen

Watermark

magick input.jpg -gravity southeast -pointsize 30 -fill white \
  -annotate +10+10 "Text" output.jpg               # Text watermark

Response Approach

When users request image manipulation:

1. Identify operation: Rotation, resize, crop, convert, effect, watermark, batch
2. Check input: Verify file exists, check format
3. Determine output: Format, quality, naming convention
4. Execute command: Use appropriate ImageMagick command
5. Verify result: Check output file was created
6. Open/display: Show result to user if requested
7. Cleanup: Remove temporary files if needed

Advanced Topics

For more advanced operations, see:

• ImageMagick Official Documentation
• Command-line Options Reference
• Examples Gallery