penwyp/claudepreference/image-converter

Image Converter

Use this skill for local image format conversion on macOS.

Tool preference

Prefer tools in this order:

1. rsvg-convert for SVG to PNG when available. It gives predictable SVG rasterization.
2. magick for most conversions and for multi-size .ico.
3. sips for simple macOS-native PNG/JPEG/TIFF conversions and resizing.
4. iconutil for .iconset to .icns.
5. qlmanage -t only as a fallback preview renderer when SVG/PDF conversion tools fail.

Common macOS tool locations include:

• /opt/homebrew/bin/rsvg-convert
• /opt/homebrew/bin/magick
• /usr/bin/sips
• /usr/bin/iconutil
• /usr/bin/qlmanage

Use command -v at runtime instead of hardcoding paths unless a command lookup fails.

Quick workflow

1. Inspect the input:

``bash file input.svg magick identify input.svg ` If magick identify cannot read the file, use file` only and continue with format-specific tools.

1. Convert with the bundled script when possible:

``bash skills/image-converter/scripts/convert-image.sh input.svg output.png --size 800 skills/image-converter/scripts/convert-image.sh input.svg output.ico skills/image-converter/scripts/convert-image.sh input.png output.icns ``

1. Verify output:

``bash file output.png output.ico magick identify output.png output.ico ``

Format notes

• SVG to PNG: preserve transparency with rsvg-convert or magick -background none.
• SVG/PNG to ICO: create a multi-resolution icon containing 256,128,64,48,32,16.
• PNG to ICNS: create an .iconset with 16, 32, 64, 128, 256, 512, and 1024 pixel variants, then run iconutil -c icns.
• JPEG output has no alpha channel. If converting transparent input to JPEG, flatten onto white unless the user specifies a background.
• Do not overwrite source files unless the user explicitly asks. Same-stem outputs such as icon.svg -> icon.png are fine.

Guardrails

• Never overwrite source files unless the user explicitly asks.
• Never assume a tool is installed — check with command -v at runtime before using it.
• When all conversion tools are missing, report which tools are needed and stop; do not silently fall back to a different output format.
• For ICO/ICNS generation, always verify the output contains the expected sizes before reporting success.

Common commands

SVG to PNG:

rsvg-convert -w 800 -h 800 icon.svg -o icon.png

SVG/PNG to multi-size ICO:

magick icon.svg -background none -define icon:auto-resize=256,128,64,48,32,16 icon.ico

PNG/JPEG resize:

sips -Z 1024 input.png --out output.png

PNG to ICNS:

mkdir -p AppIcon.iconset
sips -z 16 16 input.png --out AppIcon.iconset/icon_16x16.png
sips -z 32 32 input.png --out AppIcon.iconset/icon_16x16@2x.png
sips -z 32 32 input.png --out AppIcon.iconset/icon_32x32.png
sips -z 64 64 input.png --out AppIcon.iconset/icon_32x32@2x.png
sips -z 128 128 input.png --out AppIcon.iconset/icon_128x128.png
sips -z 256 256 input.png --out AppIcon.iconset/icon_128x128@2x.png
sips -z 256 256 input.png --out AppIcon.iconset/icon_256x256.png
sips -z 512 512 input.png --out AppIcon.iconset/icon_256x256@2x.png
sips -z 512 512 input.png --out AppIcon.iconset/icon_512x512.png
sips -z 1024 1024 input.png --out AppIcon.iconset/icon_512x512@2x.png
iconutil -c icns AppIcon.iconset -o AppIcon.icns