ss-format-convert

name

ss-format-convert

description

Convert images between formats: PNG, JPG/JPEG, WebP, TIFF, BMP, GIF, HEIC, and AVIF. Performs high-quality lossless conversion by default. Handles alpha channel transparency automatically — compositing against a configurable background color when converting to formats that lack alpha support (JPG, BMP). Supports single-file and batch directory conversion with optional recursive subdirectory scanning. Uses ImageMagick. Use this skill whenever the user wants to: convert an image to another format, change image format, save as PNG/JPG/WebP/TIFF, convert HEIC photos to JPG or PNG, batch convert images, make images web-compatible, convert to WebP for web optimization, or anything involving image format conversion. Also trigger when the user mentions format names in the context of converting, exporting, or saving images.

Format Convert — Lossless Image Format Converter

Convert any image between PNG, JPG, WebP, TIFF, BMP, GIF, HEIC, and AVIF using ImageMagick. Lossless by default — preserves maximum quality and original dimensions.

Prerequisites

ImageMagick is required. For HEIC/AVIF support, ensure delegates are installed.

brew install imagemagick    # macOS
sudo apt install imagemagick # Debian/Ubuntu

How to use

Run the bundled script:

bash <skill-path>/scripts/convert.sh <input-image> --to FORMAT [OPTIONS]

Options

Flag	Description	Default
--to FORMAT	Target format (png, jpg, webp, tiff, bmp, gif, heic, avif)	(required)
--output DIR	Output directory	./converted/
--quality N	Quality for lossy formats 1-100	100
--bg-color HEX	Background color when removing alpha (6-digit hex, no #)	FFFFFF
--batch DIR	Convert all supported images in a directory	—
--recursive	Include subdirectories in batch mode	off
--formats	List supported formats and exit	—

Supported formats

For the full reference with alpha support, lossy/lossless details, and conversion notes, read references/formats.md.

Format	Alpha	Quality
PNG	yes	lossless
JPG	no	lossy
WebP	yes	both
TIFF	yes	lossless
BMP	no	lossless
GIF	yes (1-bit)	lossless
HEIC	yes	lossy
AVIF	yes	both

Examples

Convert PNG to JPG:

bash <skill-path>/scripts/convert.sh screenshot.png --to jpg

Convert HEIC photos to PNG:

bash <skill-path>/scripts/convert.sh photo.heic --to png

Convert to WebP for web optimization:

bash <skill-path>/scripts/convert.sh banner.png --to webp --quality 90

Batch convert all images in a folder to WebP:

bash <skill-path>/scripts/convert.sh --batch ./images/ --to webp --output ./web-images/

Batch convert recursively:

bash <skill-path>/scripts/convert.sh --batch ./photos/ --to jpg --recursive --output ./exported/

Transparent PNG to JPG with custom background:

bash <skill-path>/scripts/convert.sh logo.png --to jpg --bg-color 000000

List supported formats:

bash <skill-path>/scripts/convert.sh --formats

How it works

The script uses ImageMagick for all conversions with a lossless-first strategy:

1. Alpha detection — Before converting to a non-alpha format (JPG, BMP), the script checks whether the source image actually has transparency using magick identify -format "%A". Only images with real alpha data get flattened against the background color.

2. Quality maximization — The default quality is 100. For formats that support true lossless encoding:

   • WebP at quality 100 enables webp:lossless=true
   • AVIF at quality 100 enables heif:lossless=true
   • PNG always uses lossless encoding (quality controls compression level only)
   • TIFF uses uncompressed output (-compress None)

3. Dimension preservation — The script never resizes. Output dimensions always match the source.

4. Same-format skip — If the source is already the target format, the file is skipped rather than re-encoded.

Format notes

• Animated GIFs — Only the first frame is converted. Full animation conversion is not supported.
• HEIC/AVIF — Require ImageMagick delegates (libheif). If not installed, conversion will fail with a clear error.
• JPG/BMP from transparent sources — Alpha is composited against --bg-color (default white). Opaque sources pass through unchanged.

Output naming

Files are saved as <original-name>.<target-ext> in the output directory. For example:

• converted/screenshot.jpg
• converted/photo.png
• converted/banner.webp