Image Manipulation Image Magick

Image manipulation with ImageMagick

Use ImageMagick magick commands to inspect image metadata, resize or convert individual files, and batch process images safely across PowerShell and Bash environments.

This skill enables image processing and manipulation tasks using ImageMagick across Windows, Linux, and macOS systems.

When to invoke

• "Resize this image with ImageMagick."
• "Create thumbnails for these images."
• "Get image dimensions and metadata."
• "Batch convert or resize wallpapers."
• "Process images based on width or height."

Prerequisites and context

• ImageMagick installed on the system
• Windows: PowerShell with ImageMagick available as magick (or at C:\Program Files\ImageMagick-*\magick.exe)
• Linux/macOS: Bash with ImageMagick installed via package manager (apt, brew, etc.)

Core capabilities

1. Image Information

• Get image dimensions (width x height)
• Retrieve detailed metadata (format, color space, etc.)
• Identify image format

2. Image Resizing

• Resize single images
• Batch resize multiple images
• Create thumbnails with specific dimensions
• Maintain aspect ratios

3. Batch Processing

• Process images based on dimensions
• Filter and process specific file types
• Apply transformations to multiple files

Procedure

Example 0: Resolve magick executable

PowerShell (Windows):

# Prefer ImageMagick on PATH
$magick = (Get-Command magick -ErrorAction SilentlyContinue)?.Source

# Fallback: common install pattern under Program Files
if (-not $magick) {
    $magick = Get-ChildItem "C:\\Program Files\\ImageMagick-*\\magick.exe" -ErrorAction SilentlyContinue |
        Select-Object -First 1 -ExpandProperty FullName
}

if (-not $magick) {
    throw "ImageMagick not found. Install it and/or add 'magick' to PATH."
}

Bash (Linux/macOS):

# Check if magick is available on PATH
if ! command -v magick &> /dev/null; then
    echo "ImageMagick not found. Install it using your package manager:"
    echo "  Ubuntu/Debian: sudo apt install imagemagick"
    echo "  macOS: brew install imagemagick"
    exit 1
fi

Example 1: Get Image Dimensions

PowerShell (Windows):

# For a single image
& $magick identify -format "%wx%h" path/to/image.jpg

# For multiple images
Get-ChildItem "path/to/images/*" | ForEach-Object { 
    $dimensions = & $magick identify -format "%f: %wx%h`n" $_.FullName
    Write-Host $dimensions 
}

Bash (Linux/macOS):

# For a single image
magick identify -format "%wx%h" path/to/image.jpg

# For multiple images
for img in path/to/images/*; do
    magick identify -format "%f: %wx%h\n" "$img"
done

Example 2: Resize Images

PowerShell (Windows):

# Resize a single image
& $magick input.jpg -resize 427x240 output.jpg

# Batch resize images
Get-ChildItem "path/to/images/*" | ForEach-Object { 
    & $magick $_.FullName -resize 427x240 "path/to/output/thumb_$($_.Name)"
}

Bash (Linux/macOS):

# Resize a single image
magick input.jpg -resize 427x240 output.jpg

# Batch resize images
for img in path/to/images/*; do
    filename=$(basename "$img")
    magick "$img" -resize 427x240 "path/to/output/thumb_$filename"
done

Example 3: Get Detailed Image Information

PowerShell (Windows):

# Get verbose information about an image
& $magick identify -verbose path/to/image.jpg

Bash (Linux/macOS):

# Get verbose information about an image
magick identify -verbose path/to/image.jpg

Example 4: Process Images Based on Dimensions

PowerShell (Windows):

Get-ChildItem "path/to/images/*" | ForEach-Object { 
    $dimensions = & $magick identify -format "%w,%h" $_.FullName
    if ($dimensions) {
        $width,$height = $dimensions -split ','
        if ([int]$width -eq 2560 -or [int]$height -eq 1440) {
            Write-Host "Processing $($_.Name)"
            & $magick $_.FullName -resize 427x240 "path/to/output/thumb_$($_.Name)"
        }
    }
}

Bash (Linux/macOS):

for img in path/to/images/*; do
    dimensions=$(magick identify -format "%w,%h" "$img")
    if [[ -n "$dimensions" ]]; then
        width=$(echo "$dimensions" | cut -d',' -f1)
        height=$(echo "$dimensions" | cut -d',' -f2)
        if [[ "$width" -eq 2560 || "$height" -eq 1440 ]]; then
            filename=$(basename "$img")
            echo "Processing $filename"
            magick "$img" -resize 427x240 "path/to/output/thumb_$filename"
        fi
    fi
done

Gotchas

1. Always quote file paths - Use quotes around file paths that might contain spaces
2. Use the & operator (PowerShell) - Invoke the magick executable using & in PowerShell
3. Store the path in a variable (PowerShell) - Assign the ImageMagick path to $magick for cleaner code
4. Wrap in loops - When processing multiple files, use ForEach-Object (PowerShell) or for loops (Bash)
5. Verify dimensions first - Check image dimensions before processing to avoid unnecessary operations
6. Use appropriate resize flags - Consider using ! to force exact dimensions or ^ for minimum dimensions

Command patterns

PowerShell Patterns

Pattern: Store ImageMagick Path

$magick = (Get-Command magick).Source

Pattern: Get Dimensions as Variables

$dimensions = & $magick identify -format "%w,%h" $_.FullName
$width,$height = $dimensions -split ','

Pattern: Conditional Processing

if ([int]$width -gt 1920) {
    & $magick $_.FullName -resize 1920x1080 $outputPath
}

Pattern: Create Thumbnails

& $magick $_.FullName -resize 427x240 "thumbnails/thumb_$($_.Name)"

Bash Patterns

Pattern: Check ImageMagick Installation

command -v magick &> /dev/null || { echo "ImageMagick required"; exit 1; }

Pattern: Get Dimensions as Variables

dimensions=$(magick identify -format "%w,%h" "$img")
width=$(echo "$dimensions" | cut -d',' -f1)
height=$(echo "$dimensions" | cut -d',' -f2)

Pattern: Conditional Processing

if [[ "$width" -gt 1920 ]]; then
    magick "$img" -resize 1920x1080 "$outputPath"
fi

Pattern: Create Thumbnails

filename=$(basename "$img")
magick "$img" -resize 427x240 "thumbnails/thumb_$filename"

Limits

• Large batch operations may be memory-intensive
• Some complex operations may require additional ImageMagick delegates
• On older Linux systems, use convert instead of magick (ImageMagick 6.x vs 7.x)

Output template

## ImageMagick result

**Status:** completed | command only | blocked
**Input:** `<path or glob>`
**Output:** `<path or directory>`

### Commands
- `<magick identify ...>`
- `<magick input -resize WIDTHxHEIGHT output>`

### Validation
- `magick identify -format "%wx%h" <output>`: `<dimensions>`
- Files processed: `<count>`
- Skipped files: `<count and reason>`

Quality gate

• magick is resolved on PATH or through C:\Program Files\ImageMagick-*\magick.exe before commands are run.
• File paths are quoted in both PowerShell and Bash examples.
• PowerShell invocations use & $magick when the executable path is stored in a variable.
• Batch operations use safe loops and preserve source files unless the user explicitly requests overwrites.
• Dimensions are checked with identify -format "%w,%h" before dimension-based processing.
• Resize flags such as ! or ^ are used only when exact or minimum-dimension behavior is intended.